But 'transformative work' is a legal argument. No one in many of the fandoms I'm in really thinks in those terms. What you're effectively saying is that some fan creators should suck it up and live in uncertainty, and of course, suck it up if the AO3 ever decides to pursue the enforcement of one of the rules it has already in place. Because other fan creators are getting antsy because their works can't be hosted to the archive yet. For technical reasons.

The AO3 was not an advocacy branch; its goal is to host creative fanworks in a place that will not go down. I get it, original works is not on your definition of fandom and fannish creativeness (and probably not on the definition of whomever thought that line in the first place). Well, guess what? You (general you) don't get to define fandom and fannish creations for everyone else. This reads to me as strictly a case of media fandom/journal fandom thinking their way of doing fandom is The Way.

When you (general you) say 'art and vids are fine, but they're just going to have to wait because it's hard to deal with them,' what statement does that make about art and vids?

That they're harder to deal with. The work on the art part has already begun; they've begun taking opinions for design decisions. There's no coding needed for allowing original work; it doesn't take away those people working on it. It will not slow it down.