and that's without even necessarily going out of your way to do it.
The affection stats seem to be deliberately set up so that you'll get Aerith all or most of the time, if you really don't bother to try. But that's just an impression.
As for how Cloud's feelings factor into this, I've always & continued to maintain a neutral stance, but it's very difficult
not to admit that there are some pretty heavy-handed "he loves Aerith" messages throughout the game. That said, regardless of who's "right" for whom, barring the variable of the affection scores, Cloud seems to have been paying more attention to Aerith at the time.
There are mandatory scenes that indicate feelings for Tifa, but they're all flashbacks. This isn't to say "she's a crush he's forgotten," just that, during the course of the game, he's more interested in Aerith.
I think I've veered somewhat off-course, though. My point is, he obviously has feelings for both of them. But I think it's a question of which scene seems more likely. Or...who knows? Maybe he went on more than one date that night? Canonically speaking, of course.
It might be better put that her death is set up more effectively the more attached the player is to her by that point.
Well, yes & no. While that certainly is true, the more the characters interact with the departed character, the more of an impression that it should logically leave. This is probably why no one really gives a shit about Leo in FFVI. They knew him for what, like 2 days? It's kind of a dramatic thing.