Floyd Joy Sinclair retires from boxing having never been knocked down in his whole career in 21 years. Thoughts on this phenomenal achievement? Even Marciano was knocked down a couple times.
Judah did knock him down, unfortunately not counted, and he did touch the canvas against Hernandez but only because he hurt his hand, not from a punch
Floyd has been knocked down once officially by Hernandez (although it shouldn't have been a KD) as well as once by Judah (although it wasn't officially counted). So, either way, whether you care about the official rules or about what the ref should have called, there's a single knockdown.
He wasn't hurt by a punch in either of those so yeah he wasn't really knocked down on his ass. It is very impressive when you look at it.