Dr. Apgar's "testimony" reeks of embarrassment and cuckoldry. He exaggerates just how far Riker and his wife went, and then embellishes his response to Riker, knocking him to the ground (yeah right) as if it were a kid fantasizing about beating a bully. Riker and the wife come off as horny children, and Apgar comes off like a guy who's not taking this crap. His version of Riker went down faster and easier than Worf. Nah.
One other thing - if Riker says the wife invited him to stay onboard, but the wife says Riker demanded to stay aboard, what did Geordi hear? He was there too, but his version of events don't seem to be used here.
What I think happened - Riker and the wife exchanged subtle glances back and forth, which Apgar picked up on. The wife invited Riker to stay aboard, and things got a little cozy in the quarters. They kiss. Apgar barges in, grabs his wife, Riker intervenes, and Apgar ends up on the floor. Riker tries to defuse it, but to no avail. The wife is in denial about the whole thing, because that's not something a respectable woman does.