Language at some level is really about the speaker, in terms of their background, knowledge or lack thereof, what they want to communicate and so forth. Sometimes I think what this equity language betrays is some desire to convey moral or intellectual status, or even some assertion of social power, but sometimes it reflects a genuine attempt to respect the wishes of the subjects of what they're saying.
The problem as you point out is different groups might see things in different ways, and maybe even want to be seen in different ways in different settings or at different moments. Maybe they want to be seen as strong or resilient in one setting, and maybe in another they want to discuss the injustices they have to be resilient against. I think this is only a natural part of human nature.
So it makes sense that these edicts about proper language aren't just morally problematic because they reflect some power motive on the part of the speaker, at the expense of the subject of the speech, but because in doing that, they deny some flexibility in how certain topics and persons can be portrayed or portray themselves.
The example of the passage from Behind the Beautiful Forevers is compelling in how it illustrates how equity language can be disenfranchising and therefore counter to its own stated purposes. The passage works because it is meant to convey something about the parents' perspective and to cause us to wrestle with that. The author is channeling the parents' language. In a different context, maybe the same situation might be described differently, more positively. It's not just that the language in the second version is intellectualized and distanced, it's that it denies choice of language from those who potentially are in the best position to say something about it.
There might be a worthwhile transition to a new framing that makes sense. I've heard people rip on using the metric system because supposedly its proponents wanted 10-hour days and 10 days a week, etc, which was taking tenets to ridiculous points. The problem now is trying to frame some changes in grander terms because you might well get ridiculous outcomes ( and in current society definitely will).
Does writing a guide or policing language that causes blowback provide help? If you're speaking to a room full of people and half favor this language and half don't then you've only shifted the grievances from one side of the room to the other.
There's no easy answers here, but I don't think writing language guides or policing peoples language actually accomplishes much.
Of course, it’s probably much more difficult for those who aren’t already successful and famous.
The guides are probably banking on most of the changes being accepted, however grudgingly. Of course, they may be wrong, and even if there's pushback, they may be convinced enough of the righteousness of their cause to press ahead anyway.
The reason people first language fails is because there's some subjects of this language that find the original wording insulting and there's some subjects of this language that find the new words insulting.
I have back issues. Major ones that pinch my sciatic nerve due to a fractured column that healed improperly. They've gotten to the point a few times in my life where I could not walk much less feel (at all) my leg for prolonged periods of time. If someone called me a "person experiencing a disability" it sounds like you're trying to remove the hurdle that the disability puts in my life. I already had to grapple with the idea that I am not bound to that disability. I have found ways to climb small mountains, to hike, pack, move/lift heavy things, sit, and work out all with abundances of caution and very proper form.
That's to say, codifying this language just does what the first correction set out to correct: it institutionalized language some people don't like. In a world with a big variety of perspectives and experiences, the best resolution to these problems isn't some authoritarian document telling people how to talk. It's gracefully correcting people on the way that you'd like to be spoken about and people respecting that. Nobody needs to walk on eggshells around how I'd like to be referred, they just need to meet me where I am when I make a choice.