This feels like it's worth discussing so let me offer my two cents.
Ayame's beauty is not only that she's just beautiful, which she is. Toned body with curves on the right places, yeowza! But her charm relies on the fact that she looks like the ultimate girl next door who doesn't go around sleeping with people. That is what makes all those guys want her even more.
Fujiko from what I got from the story does have a lot of people drooling over her (Scott comes to mind) but she sleeps around a lot. If you get something too easily you probably are not going to care as much for it as you did for something you had to work really hard for. That's just human nature in my opinion.
Regarding Robert, the game does explain that this is not a "what would Ayame do in this case" scenario but an entirely different universe with an entirely different Ayame which means everything else and everyone else might be different as well. Maybe in the true ending Arthur wasn't the reason why Robert's ex left, although I doubt it because of how he behaves when he sees Ayame for the first time.
I think the routes are played in a way that they aren't interchangeable so we can see a whole different side of Ayame. In that regard it feels like you're playing different games and I love this about Fleeting Iris. There's a few things that you can take for canon such as Melvin being a douchebag along with Scott and Armand. Sato and Fujiko having some sort of bad blood with Ayame (although Fujiko's personality changes a lot during Melvin's harem route!) I suspect Armand being Ayame and Fujiko's father which is hinted heavily throughout quite a few routes. The zombie apocalypse associated drug. Arthur being Jack's father. etc.
I got some inside info on the virginity state of the two spies as I too was curious and asked Starke personally. He told me that one of them was and the other wasn't. He didn't say which was which, which made me even more curious.
I'm going to guess the more mature one is the one that isn't a virgin but I've been surprised plenty of times by Starke before so take it with a grain of salt.
As for the two cops having sex in this game as a cameo, remember that the universes are connected, which means that during the True Ending they actually didn't have sex at that point and time.