The Waldstein does 360C> CS> Dash B>214A> 623C > 6C I believe. I just tried it, the first 6C doesn't wallbounce but the second 6C did.
Edit:I got it to work, it still exists. The timing is easy enough if you get a high enough launch and it doesn't seem to be character specific.
This is how I think it works, you need to do the 6C as early as possibly to grab them at the maximum height, at this point I think the hurtbox of the enemy character doesn't collide with the boundary of the walls allowing you to loop it.
In some training mode investigation it seems the sweet spot for this to occur is anywhere between 58-68frames after the initial 6C.
A potato quality video I recorded displaying it still working.
https://www.youtube.com/watch?v=P17k6_Z7d2U&feature=youtu.be
Edit2: You can also get this off of regular 360 too, only requiring 100exs & vorpal to activate it.