You do see the Japanese pros do B nail cancels on throws. Nezu comes to mind - he uses it to to get seals for FRKZ on throws. I think you also need to nail cancel for the dash -> 3C after throw?
Also, it's a perfectly reasonable thing to do. It's not like a bunch of 1-frame links, though the timing on the cancel takes a little getting used to. And it nets you more damage and oki.
And unfortunately, super jump cancels are pretty important for Tsubaki for stuff like 6CC -> HJC <air combo finisher>. Ragna, too. He has to HJC on most of his launchers to properly combo Belial Edge.
I'm terrible with inputs and having trouble with it myself ><