As I've thought about it and watched the video a few more times, what I really think we're looking at here is -- as some others have kind of hinted at -- something that changes what we conventionally think of as the traditional dark ride "form." It's integrating the guest into musical scenes that play out in full, more akin to a participatory show than a ride that progressively takes us continuously through the narrative.
I'm not ready to say if I think this formal swerve is something I like or not (especially without feeling how the ride vehicle is "dancing," as that's apparently quite a big aspect). But I do know that, as the ride's sat with me, I find some of the big, open spaces that are relatively empty to be kind of off-putting to me. It definitely works for the finale, but the first two scenes of the ride I'm less sure of.
I think it's trying to achieve something very different than either of those (with the caveat that any knowledge I have of Runaway Railway is purely secondhand, as I've not ridden it, nor have I watched any ride videos). ROTR is very much an "action" attraction, while Runaway Railway is all about projection mapping and zany adventure.
The defining features of BATB that I've taken away so far are the gorgeous (physical) sets. In that sense, it's much more a successor to the classic Fantasyland dark ride than Runaway Railway is.