You may want to read up on computer-generated random numbers. There's a reason they're more properly called pseudo-random (they're usually based on very long sequences). 'True' random number generators are not widely used as of today.To be technically correct, dice are horrible probability generators. While a computer system has an equal chance in an "if-then" situation to produce any probable value, dice have to take the force of the roll, spin, table shape, objects and so forth into account.
Don´t forget to Increase the point buy by several points. Otherwise Stats are generally lower. When you increase before buying, suddenly an 18 is 5 points more expensive than previously... An 18 from 10 costs 16 points. A 16 costs 9 points. A 14 costs 5 points.One possible variant to give races a little more differentiation would be to also set the stat bought up from 8. Not a penalty, just, this stat tends to be a little lower, but you can still buy it up as high as you like.
These correspond roughly to the old stat penalties from 1e, where aplicable:
Human: any
Dragonborn: DEX (nothing to go on, here, they look kinda bulky, though)
Dwarf: CHA (classic)
Elf: INT (4e Elves are basicly 'wood' or 'wild' elves, who had an INT penalty)
Eladrin: CON (Eladrin, are classic 'high elves,' they always had a CON penalty)
Gnome: STR (prettymuch going to be STR for the little guys)
1/2 Elf: none (you have to buy your 8 up to a 10, half elves get a good 'blend of the best traits of each parent,' so no dump stat for you)
1/2 Orc: INT (someone's gotta be big and dumb)
Halfling: STR
Tiefling: WIS (Your ancestors made pacts with devils, you inherited their common sense along with the horns)
This doesn't stop you from having an 18 INT elven wizard or 18 CON Eladrin Warlock - you just have to scrape the points together without dumping an 8 in anything else. It also means no 'clutzy elves' - if you have a bonus in a stat, the minimum post-racial becomes 12.
I still want someone to tell me why this whole change is 'adding flexibility'. I don't see that. It is just shuffling around which race is best at what. The EXACT same dynamics as before will drive players choices of race and class. The choices they end up with may be different, but how is that a better game? If players were already heavily influenced to play the best combinations then they will be still. If they were NOT heavily influenced to play the best combinations then the whole thing is irrelevant and they'll be just as happy with the old way as the new way.
The ONLY argument I've seen that really has any potential weight at all here is the one about games with heavily restricted choices of race. This is rather a corner case IMHO. It also isn't really entirely clear to me that even then the situation is really better with the new rule. It will heavily depend on exactly what races are and aren't allowed. I can see it being nice if you were excluding every race that was good at class X before and now a couple of them are better for that class, OK you may see more of that class show up. Remember though, every game has only so many PCs and all of them have a race and class. The actual distribution of races at the table is likely to have little to do with what is potentially best mechanically unless you have a lot of really serious optimizers, who are going to pick specific things regardless of what you do since something is ALWAYS best (at least in their view).
One possible variant to give races a little more differentiation would be to also set the stat bought up from 8. Not a penalty, just, this stat tends to be a little lower, but you can still buy it up as high as you like.
These correspond roughly to the old stat penalties from 1e, where aplicable:
Human: any
Dragonborn: DEX (nothing to go on, here, they look kinda bulky, though)
Dwarf: CHA (classic)
Elf: INT (4e Elves are basicly 'wood' or 'wild' elves, who had an INT penalty)
Eladrin: CON (Eladrin, are classic 'high elves,' they always had a CON penalty)
Gnome: STR (prettymuch going to be STR for the little guys)
1/2 Elf: none (you have to buy your 8 up to a 10, half elves get a good 'blend of the best traits of each parent,' so no dump stat for you)
1/2 Orc: INT (someone's gotta be big and dumb)
Halfling: STR
Tiefling: WIS (Your ancestors made pacts with devils, you inherited their common sense along with the horns)
This doesn't stop you from having an 18 INT elven wizard or 18 CON Eladrin Warlock - you just have to scrape the points together without dumping an 8 in anything else. It also means no 'clutzy elves' - if you have a bonus in a stat, the minimum post-racial becomes 12.
Ok...here's my story of "added flexibility". In a campaign I am currently playing in I made a Cleric because there were no other PC Leaders. I wanted to go melee so I did the STR build and went with Longtooth Shifter (STR/WIS). As for the build itself I focused on being defender secondary by taking both shield feats, scale, and finally plate. For RP and backgrounds there were 3 Dwarves in the party and I described my character as "Their wierd uncle" who was always showing up to family events (birthdays, weddings, etc). When I read the preview of the new Cleric build I was like...wow...I can be a real Dwarf and keep my build/concept/RP background pretty much in tact with just a few stat changes (shuffle some stats around).
Now admittedly the optional stat changes aren't what gave me this flexibility, it was the new Cleric build matching up to Dwarf stat bumps, but that doesn't mean that it can't happen. The point is that if you are optimizing then your first choice is to get a race that matches up with your class/build. By adding another stat choice to many races you've made more races compatible with this kind of matching and now you can make your choice more on flavor instead of just superior mechanics. A good example of this is the Rogue DEX/CHA build. You can go Halfling, Drow, Changeling for those stats which allows you to pick among those for your flavor. Do you want to be short? Maybe you want to be a shape changer.