Speaking of semantic quibbles, "constrain" and "limit" are synonyms. It's a bit rich to pretend they're not for the sake of scoring rhetorical points in an online discussion.
I wasn't suggesting otherwise. My statement was relating is that constraints/limits are not a separate thing from gameplay.
You can't design a game where some element of it only exists because the designer demands it exists. Such elements always fail.
Constraints applied to a game to limit its gameplay are such elements. Constraints that result from gameplay are not the same thing.
And yes, none of this is intuitive. Game design often isn't, and there's a great deal of nuance here too.
But if you need a simpler way to think about this:
Where does the decision to allow an RPG character to be customized come from? Why would one choose to make the character of their game Geralt of Rivia, versus the more generic Last Dragonborn? How does one choose to what degree between these relative extremes will be the level of customization players will be capable of?
Naturally, there is no fixed right answer, as the answer depends on the game experience you want to foster, and as such that decision needs to emerge from the basic gameplay of your game. Whether this decision constrains possibilities or not is immaterial, the gameplay is not affected, because any constraint that arises (and to be clear, every answer in that spectrum provides constraints) is fundamentally in support of the gameplay, enriching and emphasizing the game experience you intend to foster.
But there is a fixed wrong answer, and its dictating that the answer, whatever it is, is to be done for reasons that have nothing to do with gameplay. If you are worldbuilding and approaching it from a position of limiting gameplay, you are wrong.
This is taking an RPG gameworld and writing it so that choices and progression are impossible. This is taking an action shooter game and taking away all the guns, explosions, and what have you.
This is writing a world where adventurers have no reason to exist and where adventuring is punished at every turn, despite the gameplay being all about adventuring.