@nik87 @Blazing Lion
I think I figured it out.
Sandai doesn't have to break! It's grade is unknown!.
Sandai is as worse as enma but only difference being Sandai Choose Zoro and hence no recuperation. Like enma.
It's either 21 great grade because It was created in hope of copying Nidai by sukiyaki or among 12 already. I know it sounds dumb but look at it , sword is no way weak ,
Random sword which doesn't even have a grade shouldn't be able to survive Hakai impact , though I agree on zoro using Haki but still.
Sukiyaki probably thought he failed but created a master piece.