And because I feel sexism promotes and encourages stupidity, I frequently engage with others on this topic.
I really worry about the state of civilization when acknowledging that males cannot get pregnant is considered "sexism".
Believing that it is insulting and demeaning to men to be asked the exact same questions as women, including questions about the possibility of being pregnant, is sexist.
Men are not demeaned when they are equated with women, given the same treatment as women, not held separate and apart from women, etc. They might feel insulted, especially if they're male chauvinists, but having to answer the same questions on a single standard form isn't an insult.
Also, in case you haven't noticed, I have explicitly agreed with you that males with no female or intersex characteristics cannot get pregnant. But I disagree that presuming someone is male is sufficient reason to have separate sex-based pre-treatment checklists, when having a single set of questions reduces the chances of something important being overlooked. Frankly, I don't see a reason to fight to preserve the old policy except as a way to maintain traditional segregation by sex, i.e. sexism.
Once again, no presumption is in place.
Here's how your approach goes:
Doctor: What is your sex?
Patient: Male.
Doctor: Are you currently pregnant, or is it possible that you might be pregnant?
Patient:... Did I not just tell you I was male?
Doctor: Yes, but you shouldn't be offended at being asked the same questions as women.
Patient: But... I'm male. It's a stupid question.
Doctor: Well, clearly you're a sexist so there!
Let's extend that the other direction:
Doctor: What is your sex?
Patient: Female.
Doctor: Is it possible that you might have prostate cancer?
Patient: I don't have a prostate, did you even graduate medical school? Go find someone competent to treat me!