Is Square Enix really a hard company to work with? I feel like we discuss them in the context of Smash when it comes to licensing but a quick look at Final Fantasy wiki's (incomplete)
collaborations page shows that they had a lot of history when it comes to lending FF IP alone to other games and whatnot.
What's another instance they have shown to be demanding in crossovers? Like, I'm genuinely curious because I never saw anyone giving an example that isn't "Cloud came with two songs".
I believe they're very particular in how their IP gets implemented, from the content of the series (mostly) only coming from the games of those particular characters (FF7, DQ3,4,8,11) to the absolute dearth of literally any new content for FF in base (including stuff that wouldn't normally be DLC like an AT or a new FS for Cloud, or a single piece of art for Cloud's spirit), to apparently having a "no multiple Heroes" rule which, although Smash got around it, was still a thing, to clearly only agreeing to Mii waves with exclusively their content, to Cloud being absent in any CG trailer that wasn't for a SE character, to the whole VA debacle (which people credit to Nintendo being anti-union, even though there are several credited union VAs in Ultimate, like Roger Craig Smith, David Hayter, Yuri Lowenthal and Haley Joel Osment - which means it's likely something specific in their contracts that conflicts with Smash).
I also believe they are highly preferential to being DLC over base, and that could be why Cloud was allegedly one of the last, if not the last finalized for base, and why all the new FF7 content was left for DLC. Possibly why they even got two characters.
Fwiw, Nomura even said he was the picky one when it came to implementing Sora in Smash, not Disney.
"Exacting" and "trickier to handle than the others" are how I described it. And I think that fits. It's not that they're not open to collaboration, it's that they're seemingly stricter about the implementation of their IP than others. Legally, that is their prerogative.
Though it seems like there might be exceptions. 2B looks significantly simpler to work with, and my guess is because Square may take a backseat to Yoko Taro on how that character/IP is handled.