Yes, it's certainly a form of BIID.
I think a lot of us have it, but there's a strong stigma in the community, so many keep silent about it. This saddens me: we all know what it's like to feel alone and ashamed of liking diapers, yet people are so quick to dismiss others with incontinence desires.
I do feel it comes from a good place: worrying about self-harm to others. But realistically you can't just hop on a plane and get a sphincterotomy done in Thailand or something. Contrary to popular belief, doctors do have standards everywhere and will not just do whatever you want. I can't name a single credible source of someone who has successfully gone this route. You can't do it to yourself. The only realistic route to maybe becoming incontinent is untraining, which takes years, and for some of us even that doesn't work, and even then can most often be reversed if they're unhappy with the result. Hypnosis is just self-delusion, but it works for maybe 5% of people. The most extreme thing I've seen was people using homemade stents, but the worst that's happened was someone getting a nasty hospital bill to remove one, or an unpleasant UTI for a week and some antibiotics. Never heard of any long-term injuries, let alone deaths.
There also seems to be a "careful what you wish for" angle, but that neglects that many with this wish have already worn 24/7 for years or even decades. So we know about the costs, the inconveniences, the leaks, and so on. We know life circumstances can change and money can become tight. We know it makes it harder to find partners. We've thought about this every day and lived as though we were incontinent for the longest time.
In my case, I've wanted it prior to puberty. It did attach to sexual desires later, but for me the desire remains just as strong even when libido does not. I won't elaborate much but I've reduced my testosterone to having almost no libido and yet my desire for incontinence has not decreased. It's not just a sexual fantasy for me. And I am not looking for acceptance for having a legitimate reason to need diapers. I have no qualms telling people now, if I had to, that it was a medical condition. How would they know? If spotted, my use of premium AB products with patterns would betray that claim whether it was a physical condition or not.
Regardless of whether BIID is a mental disorder, the fact remains that just like our own like of diapers, we can't simply dismiss it by being rational about it. It's a part of us, and causes us distress every day. Doctors realized with gender identity that the risk of harm from hormone replacement therapy (liver failure, cancers, tumors, osteoporosis, blood clots..) and gender reassignment surgery was outweighed by the mental anguish of the condition. We got there because it was common enough in society that they were forced to confront it regularly. Even still, it's hard to find doctors willing to help, but it can be done. There's a doctor in Michigan that does orchiectomies for a flat payment by informed consent alone.
Unfortunately for us, this form of BIID is not nearly as common, and it's much easier to just write us off as crazy. I've never heard of a single doctor willing to help people like us.
Yes, it is possible someone with this desire could get it and then be unhappy with the reality. "The grass is always greener". But the same can be said of gender transitioning, and that same regret can and does happen there too. We can either live in a world where we have our own autonomy and we are responsible for our own actions and possible regrets, or we can live in a world where other people decide what is best for us. I'd rather live in the former, but regrettably we don't.
Finally, my chaos theory: I don't see being continent as being in control of my body, either. Continence is the body automatically clenching sphincters shut. It is an almost insurmountable challenge to reverse this behavior. Incontinence is just the opposite condition. But true autonomy and control would be being able to switch between staying clenched or staying relaxed on one's own. If I could reach that state, I'd be happy as well. Obviously, muscles would still atrophy from non-use, but could also be retrained through kegel exercises if you went too long in the relaxed state.
To me, it doesn't have to be permanent. But I don't want to be woken up at night or wake up in the morning with a full bladder. I don't want to realize I've been holding for hours and then end up flooding and increasing leak risks. I don't want to expend mental effort on this to start the process and try to stay relaxed all the time. So to me, I don't feel in control of how my own body functions, and this causes me much distress.