iserith
Magic Wordsmith
I think this is a fair concern. I've seen my share of restrictions and rules changes that are not so much based in thematic concerns as they are in misunderstanding the rules or how the game runs or trying to make the game fit something it's not designed for.As a DM, it's less that a DM couldn't handle when using character creation restrictions as it is more that extreme restrictions are often indicative of the DM departing heavily from base D&D assumptions.
No every DM knows how to do that. Most don't if they haven't recieved help, aren't experienced in the edition, or aren't using a book written by someone who is.