That's right. It looks like the two adult characters did physically get on top of her, restrain her, and put weight on her. Of course there could have been some cinema magic in place to protect Maddie, who was a child, from being injured, but it looks a lot like they put at least half of their weight on the poor girl and even that could have seriously hurt her or started to suffocate her. Did she have a hand signal to tell the crew that something was wrong and she needed the scene to cut? Wait, her hands were restrained. How was she supposed to communicate that she genuinely needed help and wasn't just pretending to be panicked? Restraints like that could have made speech very difficult, maybe impossible. So yeah, Maddy very much could have been in actual danger.
Considering how little Sia seems to care about putting people in danger with what she's portraying, I wouldn't put it past her. Doing this safely would have required careful planning and a lot of effort she seemed at loathe to put in.
People are right to point out the use of dangerous restraint methods in Music in the context of its impact on the autistic community, but I'm also concerned about how they actually filmed it? Like maybe I'm missing something, idk a lot about filming movies and such, but if they actually did that restraint, doesn't that mean Maddy Ziegler was put in danger?