Mine does not, so not all Kubota's have the fast dump.
Fast dump is a regenerative function, which is really cool for some things.
They apply pressure to both sides of the cylinder piston which effectively reduces the piston area to be equal to the rod area. But it only works in one direction. And although it is faster, it is weaker, which matters little when dumping.
It's also a handy trick for some air rams, but sometimes when I use it, it's scary fast, making a 3000lb weight fall faster than free fall. I once was directed to make an air ram move as fast as possible by corporate. I checked...really?! No limit?! Faster the better was their reply.
They were shocked and a bit frightened by the result!!!