Hriston
Dungeon Master of Middle-earth (He/him)
Point buy is more meaningful in setting your power level, not less. You can literally point buy 3 15's in the exact stats you need for your class and concept. The odds of getting 3 15's or better when rolling is much lower than the 100% of point buy.
Those three 15's are offset by the three 8's you're forced to take along with them, making all choices available through point-buy theoretically equivalent. You may disagree, but I think that's the intent behind the system, not that everyone is going to pick the one, most optimal option. Also, it's only 100% if you choose them, a choice which is available to anyone else who's also using point-buy, remembering there are 64 other arrays available.
We've been talking about rolling, point buy and array with respect to world build(general population) for the entire time. So yes, when you moved the goalposts to stances, I moved them back.
We've also been talking about player decision-making vs. randomness, but you don't seem inclined to address either of my arguments, so I'll move on.
There's no other method it could be referring to.
Of course there is! There are many other methods for rolling ability scores (some of them have been talked about in this thread), and there is no constraint placed on the DM to use any one of them, or prohibition against devising new ones. 5e is a game which gives the DM full latitude. This should be assumed and kept in mind in specific cases when it isn't stated directly.
First, it's false to say that it only gives a system for rolling the scores of adventurers. The method in the PHB is not only for adventurers and that fact proves your statement false.
Citation?
Second, 5e is meant to be a flexible edition, but it cannot expect people to go to other editions to answer questions it creates. That's design of such incredible crappiness, that my 4 year old could do better. An edition has to be playable in and of itself or it's junk. For 5e to be playable in and of itself, it has to answer the question of what rolling means when the DMG talks about it in the NPC section.
I'm sorry you're so dissatisfied with the current edition.

The words "paramount importance" are irrelevant to my point and focusing on them is an evasion.
Well, then you've failed to understand the context of what it is you've posted.
You've been claiming that anything the PHB does that talks about adventurers, is for adventurers and not commoners.
I've made no such claim. I think it's clear, though, that adventurers are not commoners, and commoners are not adventurers.
You realize that you're arguing that the DM and all his NPCs(other than adventurers) and creatures have no access to anything in the PHB, right?
No, I'm not.
It's abundantly clear from the way other books access everything in the PHB, that it's a fact that everything in the PHB is not just for players or adventurers. But by all means, keep harping on "citations".
You asked me to cite "rules" to support my claim that step 3, along with the other steps in Chapter 1, is specifically intended for the creation of adventurers. I've done that. You, on the other hand, are unable to provide a shred of textual evidence that supports the claim that any NPC that has rolled ability scores is meant to have its scores rolled by the method given in step 3.
There quite literally cannot be another set of PCs in the same campaign that has scores outside of the 8-17 range. The PCs you are running the campaign for are the only ones in it. By definition, every other being in the campaign you are running outside of the one party of PCs, is an NPC.
Now, I suppose you could mean campaign setting and not campaign, in which case you could be running the game for multiple groups of PCs, but even then the only way to have stats outside the 8-17 range would be to allow rolling for at least one of those groups.
I'm using campaign the same way the PHB uses the word, i.e. "an ongoing story". A campaign can span generations of PC groups and multiple settings. Or you could have multiple campaigns that take place in the same setting. Anyway, I haven't misused the word, and I know what I mean by it.
My point is that point-buy has no bearing on the distribution of scores in any characters other than those who are created using it. And of course some PCs could be created using point-buy and some using dice-rolling. Why not?