Why would Ivy's 4B break? This only works for specific moves. And it is pretty glitchy, cuz moves like Ivy 2B and Hilde 2A+B can break like this, but FC B or FC A+B doesn't. So you have to do basically WR 2B/2A+B (or the other methods shown)
This may seem pretty new, but as I noticed a year or so ago, Dampierre has access to this via FC 6B. I don't really see it as a glitch, but rather as a FC added property, I dunno.
So have you tested this in a real match as well? If so then this is a pretty cool discovery, and might be really useful for the characters that that have a heavy guard break game. Cool stuff man =D