No, it is literally the same thing.
It's not. That's the point I'm making. It simply
is not the same. You can insist it is all you like. That does not make it so.
So if you think my examples are outlandish strawmen, then provide what you think isn't? Because it is possible that we do not actually disagree on this that much, given that you actually seem to think the limitations I've used as an example are fine.
I already did. "Things present in the PHB." It would be like complaining that a person couldn't be a Sith (species) Jedi in Star Wars, or a Gorn science officer in Star Trek, or a female dwarf warrior in Middle-Earth, etc.
Gorn exist in Star Trek. Worf and Nog prove that it is perfectly possible for non-member species to join Starfleet and become respected officers at prestigious appointments. (The Enterprise-D is, explicitly, the flagship of Starfleet. To be appointed both Security and Operations Officer on the Enterprise is an
extremely prestigious thing.) We have good reason to believe it could happen, and no reason to believe it can't happen, even though historically, as far as we're aware, it hasn't happened.
Sith are a humanoid species in Star Wars.
Most of them learned and practiced the Dark Side of the force, but there's nothing preventing them from practicing the light. Especially if they were found as a child and taken in by the Jedi Order. Nothing prevents it, it's just not represented generally.
Female dwarves explicitly exist in Tolkien's work. We get some kinda questionable justifications for why they either don't go out amongst other races or, apparently, aren't distinguishable from male dwarves in the rare cases they do. Nothing prevents it--it's just not represented in the stories.