agree that study hall for upperclassmen is even more useless than practicing red categories.
what newer folks should understand is that historically, people understood that 7 minutes was required in those red categories, and people were burning a TON of minutes when there was important other stuff to do (black cores to grow and such). this related to a true but highly misleading exchange a coach had with an admin at some point, that went 'how many minutes are REQUIRED to ENSURE i never lose points in a rating?' (emphasis is mine, and i am paraphrasing). answer: '7'. so the push for 0 minutes is really relative to that.
to clarify the above, the admin statement is true - a one work ethic player with 0 minutes played, will decrease on 6 minutes of practice, but will increase at 7. well, i assume that is true, it seems true, but i've never actually had a 1 WE guy with 0 minutes played. meanwhile, an 80 work ethic player who starts, those guys could grow in categories even at 0 minutes practiced. so the minimum minutes required to not lose in a category - its really relative to the player.
the actual truth is not that 0 minute reds won't drop. its that they generally won't drop much, and so there's more value in practicing stuff that can grow. the rate of growth on a category is based chiefly on the minutes practiced, minutes played, work ethic, and critically (which folks may not realize), the distance to the max rating (how much growth is left, or colloquially, potential). the rate of decrease in a category is not some mythical other concept - it runs off the exact same logic and curve that increases run off of. so when a category is an 81 on an 82 max, you basically can't grow it more than like .2 or something. it doesn't matter how much you practice or play or how high your work ethic, your rate of growth is going to be super slow. but similarly, you can't really drop it by more than .1 or something. those 79 on 82 max, those actually grow and drop MUCH more than an 81/82, on a percentage basis. perhaps even three times faster. but still, dramatically slower than a 62 on an 82 max, and if you are losing .3 instead of .1 on a 79/82, in absolute terms, its still not a big deal.
the thesis of the argument about 0 minutes - which i generally was the main pusher for - was that the forum fact about mindlessly putting 7 in maxed out categories was absolutely horrible, and mindlessly 0ing reds was a *vastly* better strategy. but if you want to really do things right, you are always balancing the returns on your investment in the practice plan. when you have a blue core, 0ing the reds is sort of a no-brainer, although i might not for example, 0 out a 90 on a 93 cap perimeter rating, on my lead per scorer, because its too important. but when you don't have much to do, you go back and try to get that last point or two (or three) out of those red ratings. still focusing on cores, of course!