To be fair to your point though, cluster HST is quite similar to max-stim. One of Dan's main points in max-stim is to keep the rep total constant while load increases, that way you have progressive load AND progressive work. Both of which are THE key stimulators of hypertrophy. So it doesn't matter that much if you use 20 reps with m-time while progressing load or do 3x7, 2x20, 4x5, etc....
...EXCEPT that m-time allows you to keep going progressively higher in load. In the above example, you could go from 4x5 to 5x4 to 7x3 to 10x2 and you would end up back at max-stim with 20x1 at the end of the progression!
The other advantage to m-time is to keep fatigue accumulation minimal which should allow greater force output, i,e,- stronger muscles throughout the lifts.