I guess I will give you my opinion.
Not only do I think it is perfectly fine for the 4.0 guy to hit directly at the woman at net as hard as he wants, I get a little annoyed when my own male partners refuse to send anything to the woman and play only to the guy.
See, if my partner is choosing to hit at the opposing 4.0 woman at net, he has to do it off of the serve or groundie of the 4.0 guy. When guys try to target me in that situation, they often miss long or wide or into the net. 'Cause it is hard to change direction off of my partner's ball and bust a ball at or by me without missing as many as you make.
Anyway, I wasn't there, so I don't know exactly what was going on. I believe my friend's 4.0 male partner was being outplayed because the other 4.0 was stronger. So he decided to win points against the woman at net by hitting returns and groundies to her. Alas, this did not work because she often ducked and his ball went long.
-- Random Error Generator, Version 4.0
-- Master Moonballer