>>34428842eh, we can see how rare non-Holo collabs are for HoloEN talents (actual 1-1 collabs, not circumstantial stuff like being on the same con panel, etc.), you can almost count them on one hand and they only happen few and far between.
Sure, the reason could also just be that most other HoloEN talents are fine and happy just staying within the comfy Holo bubble and actually don't really want to collab outside at all. And Cover is of course perfectly okay with it staying that way, as the top dog agency there's little benefit in giving their audience basically free advertising for the competition by making your fanbase unnecessarily aware that other vtubers outside the walled garden exist.
So yeah, while outside collabs (within reason) are possible, I doubt that they'd get done "in five minutes". There's probably enough buerocratic management red tape to go through that the whole vetting and set up process takes weeks in advance, and unless the talent reallyreally wants the collab for personal reasons (like, what non-Holo collabs did we have? Mori with Milky who was an old friend, Mori with IM because idk twitch, Bae with Miori who was an old friend, and Kiara with Nyan who was just an ersatz Vei), the effort it takes to get it approved is probably so prohibitively high that most talents just don't bother because they don't really care enough about non-Holos.