Fayth: Well look at that. My thought process seems to have been entirely wrong. Funny, cause I repeatedly initiated that dialogue to make sense of it...
No, your thought process is a lot more normal than the others who said it's because he brags. You don't say what Triss did unless you've actually seen it. That said, seeing as pissing on the streets seems to be a fairly socially acceptable thing to do if the residents of Flotsam are anything to go by, Triss likely saw Shorty's pecker in a non-sexual way.
Anyways, to get back to the topic on hand, no, I don't believe there are any other sexual encounters. The whores don't count. Sile can be flirted with, and she can even flirt back, but I've exhausted every combination of pre-Kayran persuade check flirt with every conversation choice you can have after the Kayran. She certainly sounds very interested in a few of those, but nothing ever comes of it. I also made sure I went the Roche path to see if there were more conversational choices there that might lead to something. No dice. In fact Sile has very little to say in Act 2, which was kind of disappointing, and she's certainly not looking for some action in Act 3 when you meet her.
So, yes, W2 is far more prudish than the first game, but since the story as it will likely continue on into W3 is starting to look like it may come full circle to Geralt finding his way back to Yen, and having to deal with the strange three way relationship the two sorceresses have with each other and Geralt (Yen's magically induced love of Geralt, Yen and Triss being great friends, Triss always having loved Geralt, Yen not really appreciating Triss loving Geralt, Geralt loving Yen, but also having spent some lovey dovey time with Triss, not to mention all the time now spent in the games Geralt has now spent with Triss) it's probably a good thing that they got rid of all that extraneous random sex from the first game, so as to better emphasize this stuff in the next game.