IIRC I had a katana cavalry unit kill 775 routers in a battle which was post-patch.

And in my current Hojo campaign I am still picking the continue option after the enemy rout and have my general (not in a position to recruit cavalry yet) chase them down and the size of the surviving enemy stack does seem to be reduced as normal compared to what it would be if I didn't give chase (i.e. I've seen outsized Ikko Ikki ashigaru units rout after getting only a few casualties and then chased them down - and as you'd expect whatever units are left in the stack that retreats from the battle are reduced to fragments which they presumably wouldn't be without the pursuit).