What the person wrote was
The core rule set does not allow me to play a true character of my choice. The 4th Edition rule set simply doesn't account for the fact that a character in the game may have an entirely valid, real set of reasons and motivations for no longer wishing to be a sorcerer, and instead wanting to focus completely on a 2nd class . . . and a 3rd class on top of that.
It appears to me that he is clearly discussing the mechanical representation not the personality.
My issue is the following:
Let's say in a campaign, Billy the Sorcerer discovers some things he's not comfortable with in terms of who he's receiving his Sorcerer-ite training from. In fact, his character meets a monk that he respects highly, and Billy (being played true to character by a good role-player) decides he'd rather commit his time to the path of monk-like enlightenment. But along the way he also discovers that he is very much interested in studying battle tactics, and so takes up with a warlord for a while to study battle strategies.
Again, for the types of campaigns I usually play, these are not at all unusual types of choices for characters to make--who do we associate with? Who do we train with? What are the motivations of Organization X? What if, as a sorcerer, for philosophical and moral reasons I decide I want to discontinue studying sorcerer, but don't want to give up the lessons I've already learned? These are valid, character-driven decisions that will also directly affect the TYPE of character that they ultimately become
This is not unlike my own "real life"--I have backgrounds in several academic and vocational subjects, and enjoy pursuing knowledge in all of them.
The problem with using his "real life" as an example is that he assumes that characters in the fantasy setting are going to have the opportunities to learn as they have in the our world where you can take a course at the local community college or annex, go to the local corner McDojo, etc and that transportation is available to get him to all of these places in between adventuring and that training time is minimal to non-existant (unless you have large portions of downtime between adventures). It also assumes that all trainers wouldn't require a time commitment and would allow people to come and go as they want before their training is complete or would not have other requirements
Before the 1960's, learning Kung Fu in America required you to at least be Chinese unless the sifu was a close family friend. Also, qualtiy masters were often selective about who they woulld teach- from the selection process where students waited outside the Shaolin Temple to the switching between masters, often requiring a letter from one sifu to another stating the quality of your character and level of commitment).
Imo, it also doesn't help his case that, after using his "real life"as an example, he proceeds to dismisses anyone arguing that multiple classes is not "life like" with "Bullcrap. Since when did a "roleplaying game" hamstring a player to actually play a true-to-life character concept? Well, in D&D's case, since about June 2008, because it's simply not allowed in the CORE 4TH EDITION RULEBOOKS."
Um, how about the training rules in 3e? What about the 3.0 skill sidebar saying that DMs may restrict taking ranks in appropriate skills (e.g, swim in the desert).
I may not particulary care for 4e , but one of the things that I think they got right (for the most part) was heroic tier multiclassing. Not that it is t hard to get rid of some of the 3e multiclass front loading to reflect a more piece meal training with a couple of simple house rules