High reps can be a good idea, because what everyone's missing is that what's needed to grow is increased intensity, not necessarily increased poundages. Increased poundages is only one avenue, others include intensity techniques like supersets, tri-sets, giant sets, rest-pause reps, forced reps, cheats, negatives, reduced rests between sets, etc. that don't involve increased poundages.
Exactly what Coleman, Larry Scott & Milos prescribe as parts of giant set or tri set routines some of the time, which amounts to high reps.
Plus, some denser muscles respond better to high reps, like delts, calves and forearms.
Plus the change-up from lower reps shocks the muscles.
Soreness can in fact be a good indicator of growth-no one can say for sure actually. Secondly, with DOMS there's definite confirmation you've hit the desired muscle area. Combine those two factors and i'd say you're far better off trying for soreness as often as possible, in the absence of conclusive proof either way.
Sure, sometimes the reps can get too high with too light a weight, but i don't think this is the case here. If 30 is too high for some, 20 might not be.
