I'm pretty much going on the assumption here that in such cases, the sleeping person is expected to wake up nearly immediately - if for some reason the sleeping person is so fast asleep that they just keep sleeping, it does rather start to resemble sex with a blow-up doll.

That also goes for the Assange case - I'm operating on the assumption that the woman woke when he started doing that and, presumably, told him to knock it off.

The little Wikipedia research I've done claimed at one point that the victim later amended her statement to saying she had been "half asleep" rather than "asleep", which fits well with my interpretation above. Of course, it might be best not to blindly rely on that.

I don't think it's nonsense to be bothered about the notion of people being accused or even convicted of rape when they were understandably convinced, based on reasonable grounds, that it was consensual. Of course, "reasonable grounds" are impossible to define, but then that's why it's a grey area. Obviously in general it's about consent, not refusal, but in cases where there are "reasonable grounds" to lead one to conclude that it's consensual, it's important for the non-consenting partner to make that refusal clear. And having previously had consensual sex does change one's frame of reference, changes how explicit a consent you'd need to reasonably suppose that sex is welcome.