Does that mean this player is still a self-rated 4.0 as far as same-sex league play is concerned?
No, you only have one rating, not different ratings for different league types. Right now, his rating is 4.5 M. If an M-rated player wants to play adult, he has to slef-rate for adult but cannot self-rate lower than his M-rating. Like any other adult self-rate, he can appeal the self-rating. This is not an automatic on-line appeal. Self-rating appeals are the type that you make your case to an actual person and that person decides on the merit of the appeal. In this case, I beleive they would (or should) grant the appeal. Middle States, in my experience, has been pretty fair about granting appeals, although they have been tightening a little in the last year or two, so you never know.