even low volume low rep Doggcrap training suggested upping your normal 3 rest pause sets of 8-15reps to 20-30 total for bis and tris. but I agree. I never did it. I kept ho the same 8-15 with better strength gains.
1) Kai's a freak of nature
2) It's a video - not necessarily a factual representation of what he usually does.
3) Let's say you do 3 x 8-12 reps to make muscle. Then doing a nice pump set of 20 reps will get the blood in there, remove toxins, make you feel good and make you feel good.