The author of the LN that this is based on pretty much uses every RPG/Isekai/Gender Bender Trope in the book. So yes, but it's done for humor, in the oddest and clearly insane way possible.
Yah, it is highly possible, unless Japan has it's own 4chan, because this guy follows the concept "doesn't matter if they re cute" to the "Channer" degree
Alternatively, the author wanted to write a fluff piece about a rather average dude becoming a cute girl, something that science says no to IRL and thus is fun to write about - and is a concept that has been done to death at this point but w/e.
Starts off REALLY stupid tbh. How can you not hold in a shit that you start feeling only just then? Are your sphincter muscles so weak? I mean, maybe if he had diarrhea/sickness sure, but it didn't say such.