This has happened to me a few times, I'll get pushed off the platform and instead of returning me to the boss fight platform I'll fall onto the base floor with smoke/tentacles and die.
I don't think it's a bug in that it only happens if you're already near the edge of the platform such that you get pushed farther, well outside of the "rescue" zone. It seems to be intended to punish players for ignoring the mechanic or failing to close distance prior to the push. Eg you can see that because you're so far away to begin with, you get thrown extra far (in this case you should have stayed in tree form to protect you from the push since it was coming up).
This is the only video I have but I've been pushed off the ledge while being closer to the middle and same thing happened
I don't think this is a bug. If you had stayed in the tree you would not have gotten pushed off. If I'm a tree or rock before hes about to push, I stay until after.
AV, respectfully, the punishment for ignoring a mechanic is usually a knock down. You are given one extra life to not repeat a mistake. I don't think it fair to assume that it is intended that you are knocked out of the fight completely for missing one mechanic, there are a lot of things that go wrong, or right in these fights. As you are aware, RNG is a big part of it. And even then, sometimes you just lunge the wrong way, or a split second too slow, or you come out of a rock form too early... I have had this specific problem happen to me. It doesn't happen often, but when it does, it definitely hinders the completion of the raid unnecessarily and unfairly.
I'm not saying being pushed off is the bug, I'm saying being knocked all yhe way to the floor without being teleported back to the boss fight platform is the bug.