So I found this desync by accident, it is probably known, but I have found some legit applications.
Basically, when I want a little space, I will just dash backwards, jump, then press in the direction I was originally facing, let go, then press b, all quickly. The result is synced SH iceblocks forwards, while I am fading backwards. Well, if you switch the jump and the pressing of the direction you were facing, and it resulted in popo just doing a dd and nana doing a SH iceblock.
This can also be used with blizzard. Dash back, dash forwards and right as you do that, jump and downB. The timing seems trickier, but the result is a beautiful little blizzard desync without any roll, spotdodge, or sheild, and it is faster, requires less ground, and is telegraphed even less than the dd blizzard.