Yeah. Pretty much. I'd rather focus my time and energy as a GM on the actual adventure I'm running and keeping things fun and interesting for the players. I'm generally plenty willing to handwave stuff like "how the heck did your character get here?". As long as the character fits into the setting, and the player can come up with a reasonable explanation, why the heck would I block that? That's effort spent making things less fun and interesting for the players, which is kinda moving in the opposite direction.

That's not to say I wont put my foot down if a player comes up with something completely incompatible with the setting or adventure I'm running, but that's pretty much the only hard restriction I put in there. A player asking me to let them play their Jakaleel the Witch character in the aforementioned "Folks working for/with an Orlanthi tribal organization", would likely be met with "Um... You do realize that they will basically kill you on sight, right? Maybe save that for when we decide to run a Lunar campaign...".

Then again, if you can successfully hide such things, then maybe? I did once play a Krarsht initiate as a character in a land mostly populated by Storm Bull and Orlanthi. That was... tricky. But even with that one, it was the result of a specific GM plot/adventure (some characters who were somewhat evil/chaos, arriving to try to prevent something far more evil/chaotic from happening, while also trying to conceal their own nature/origins in the process of trying to help and work with folks who would normally kill them on sight). The real trick came with figuring out how to continue playing the character, in that same area, after the original plot was resolved.

I'll usually warn and try to wave off PC ideas that wont fit well (they "fit" into the setting, but in a way that will likely get them targeted, possibly by their own party members). But if they really really want to do this? I'll consider it. I do tend to frown on inter-party conflict though, so if they're doing this to create disruption, I'm going to push back hard. But if they are making an effort to "figure out how to make this character actually work in/with this party", I'll let them try it. But yeah, just like with running an assassin in a party with a paladin, if the PC actions force a confrontation and give the other party members no reasonable out? That may not end well.