1. I'd disagree, the details of the culture itself don't make Zandalari fit with the Alliance.
2. Regardless, they're too cutesy aesthetically.
3. Lots of races on the Horde are spiritual too. Large permanent city isn't that big an issue one way or the other. I'd go so far as to say that the clothes and architecture (admittedly I've only seen the one image with the snake temple) style fit more on Horde than Alliance.
4. Tbh I feel they'd be a good way to bridge the Belfs with the rest of the Horde with that "High beast man" race archetype.
Whereas on the Alliance I feel they'll just be another race added to try and flavor them but ultimately getting sidelined, the way the Worgen and Draenei were initially.
They don't really fit beside Draenei, Nelfs, Humans, or Dwarves.
Whereas they'd look pretty natural beside the Zandalari, Darkspear, or even Orcs and Tauren.
5. Yep I'm the same Skytotem.
I know they're the same type of creature, but the distinction is still meaningful imo.