Bloke's perspective: anal sex abso-fcuking-lutely 100% requires separate consent than vaginal sex does - 200% even, and it's mind boggling how anyone could not realise that, but there are people out there who for whatever reason just do not get it.
Sure, it can happen accidently, some positions are more prone to it than others. That's one of those things that can be a real passion killer/moment spoiler for both/all parties - depending on the situation you might have to stop and change the condom, or the bloke's off for a scrub in the bathroom (don't try to hurry that process by using hand sanitiser on the blok... look, just take my word for it, ok?)
It can also happen "accidently", which is bone fcuking stupid. The feel of it, the sensations are entirely different in every way - in that situation it feels as different to the bloke as it does to the woman, there's no way you can mistake one for the other or "not realise". That's just an "excuse", a "cover story", even an attempt at gaslighting for some cunt who decides "eh, fcuk it, I'll just assault this person and act dumb if I get called out for it".
Consent is, or rather can be, a nuanced thing, a very situational thing. Like a long term couple might be comfortable with "unless I or you specifically says 'no' to something, just go for it". They might choreograph everything before hand, or do it the same every time, or talk about it while it's in progress. Or maybe they use non verbal cues to clearly show what they'd like to do or have done to and gauge the other's reaction (Which really is one of the fundamentals isn't it? Like if you're not aware of or getting anything out of the other person's/people's reactions surely you're better off just having a swift Barclays, right?). With someone new it's obviously a different kettle of fish - people of both genders can't just assume that other people will enjoy or a comfortable with giving/receiving the same things they enjoy.
Ultimately though, with M>F anal and consent there's two key points: The first is that if a bloke is not confident, comfortable, and close to say out loud to her one of the million ways to say "I desperately want to fcuk you in the ass" then he has absolutely no business whatsoever even eating that girl's ass, let alone fcuking it. The second would be to fire a "Johnny Rambo Hyper-Realistic 14 inch Pleasure Penetrator with Realistic Throbbing Veins" so far up his ass that it crosses over from "anal sex" and becomes "large intestinal sex" - then ask him to express his views on consent...