Absolutely! Multiple have said it is never acceptable, for any reason, to have any discussion actually at the table.
And the survey says! Bzzzzt ... misrepresenting what people have said! I've stated, as have others, that we'll table long discussions until after the session so we can keep the game moving.
This effectively nixes the vast majority of possibilities of discussion, particularly because in my experience, even with very good DMs, discussion outside of game is akin to Mr. Sopwith's description of how many camels he's spotted: "Nearly...ooh...nearly one." "Nearly one?" "Call it none."
Several others have openly rejected any possibility of even out-of-game discussion in past threads. One has said, repeatedly, that they know every territory, polity, and faction of the entire world in which their campaigns occur. It literally isn't possible for any PCs to come from a "ʜɪᴄ ꜱᴠɴᴛ ᴅʀᴀᴄᴏɴᴇꜱ" type region, nor to be any sort of one-off experiment or the result of an accident, nor any other possible way a being could be anything other than one of the races they have established...even though (by their own admission) the players have never been to several of those regions, know nothing about them, and have no possible way to have learned the slightest thing about those places.
There is absolutely a strong antipathy for ever sitting down, hearing what the player has to say, and sincerely working to find a resolution that would please both parties. In some cases, to even ask for it has been likened, I kid you not, to being an outright terrorist trying to destroy the DM's "vision." I can't recall if it was "terrorist" or "saboteur", but it was definitely one of those two words explicitly used to refer to players who dared question anything about the setting or options not explicitly included.
Since the campaign world exists in my imagination (with certain established lore written down or explained verbally to a group) of course I know everything about my world. If it had not been recorded in lore then I fill in the details as necessary. When deciding what species are allowed the level of detail is not very granular. It is, however established written lore. Same way that I know a city exists, but until people go to that city and seek out a blacksmith, the specific blacksmith has not been established because there was no reason for me to establish that particular lore. On the other hand, go to any given city and look for a car dealer they don't exist because cars don't exist in my world.
The DM creates the world, the character interacts with the world via their actions so they don't get to dictate any hidden valley or lost city where their PC comes from.