It's not a coin flip when at least other player knows what he's doing. Now it's both just guessing what's gonna happen lmao
There are definitely examples of cross ups surprising even the attacking player, for sure, won't argue that. However, those are generally more rare than intentional cross ups.
Even with green lantern, one of the most cross up heavy characters, I intentionally cross up or not. Like with the b13xxtraitxxLM setup. I use f2 to put myself in that f3 ambiguous range, but based on a slight step forward and even the timing of when to press f3, I decide whether to cross up or not and believe me, it's very conditioning heavy.
Doesn't change the crux of your point though, that there are many examples of a player crossing up that didn't intend to, or a player trying to cross up and not, yet still converting. Luckily though most characters have directional inputs for strings and launchers though so it's very easy to drop combos after a surprise cross up/same side attack. Except for batman...that's just bullshit lol