Firstly, the company overseeing the tld gets to make its own rules. For example, you'd have to go through Verisign at some point if you wanted a .com domain.
Second, the only things encapsulated by the term LGBTQ are sexual orientation and gender identity, two innately connected concepts. People can add as many letters to the acronym as they want but it doesn't change anything about the movement or the group as a whole.
The point of the "more letters" is probably not what you think, but rather what if the entity in charge decides to add a new one (say, X) but it turns out the L, the B and the T now feel alienated by the X? Or, conversely, what if they decide not to include some new group (say, P)? It just seems rather nebulous and down to the whims of some mysterious entity with unclear motives.
There is no "entity in charge" of the LGBT acronym, no central authority approving, adding or removing letters, or any particular concern over "alienation" from adding or removing letters. It's a cultural idiom, not an ISO standard.
Regarding its "nebulous" nature and "motives," quoting from Wikipedia[0]:
The initialism, as well as some of its common variants, have been adopted
into the mainstream as an umbrella term for use when labeling topics
pertaining to sexuality and gender identity.
The initialism LGBT is intended to emphasize a diversity of sexuality and
gender identity-based cultures.
Note that, while the quote mentions "LGBT" specifically that description also applies to the "common variants" also described, including LGBTQ, LGBTQIA, and others mentioned elsewhere in the article. I only point that out because one of your flagged comments mentions how alienated and confused you are by "the whole gay thing," so I wanted to be as clear as possible.
And if you're instead talking about the registrar, they're not a mysterious entity, and their motives are clearly spelled out on their policy page[1].
I still don't understand what exactly your concern is. The TLD doesn't even contain any elements of the LGBT acronym, yet you seem deeply concerned about them altering it willy nilly and this having some widespread negative effect on the gay community.
This despite going through the unnecessary effort of making an entire, completely off topic top level comment announcing how confused and alienated you were by the gay community and how you wish they would just stop being so visible so you didn't have to think about gay sex all the time.
I mean, I'm sure the gay community appreciates your concern and apologizes for the inconvenience, but it seems like you're trying very hard to start a tempest in teacup without even any tea to stir. Don't worry, the gays will be fine.
These days this is gauged by the level of social media outrage, this is what brings 'problems' to the attention of decision-makers, and I suspect that this rule will mostly be used as a response to that unless the domain name itself is obviously disparaging.