i am generally a pretty aggressive study haller (meaning i do very little), but i think for redshirt freshman there is actually the best logic of all cases for the 'get it out of the way early' approach. the reason being you have that 2nd freshman season, 2nd year freshman do grades like 1st year freshman, except i think its now based on college GPA like it would be for a soph. but i mean, the curve of dumbness if you will, which is worst for freshman and gets much better over time, the redshirt freshman have that freshman curve twice. its just the second time is based on college GPA.
overall on this GPA stuff, you really only have two reasonable approaches, and as long as you are doing one of the two, its fine. either put a moderate amount into freshman and then 0 upperclassmen, 'the safe way', or cut it close the whole way (with occasionally upperclassmen SH for exceptionally dumb players, in the 'safe way'). the second approach is probably optimal, strictly speaking, but the penalty for missing a player can be quite severe, and there's nothing wrong with contributing a few freshman minutes towards your own peace of mind later. especially if you don't check your teams every game cycle. so its really like, there are two reasonable paths and as long as you take one, you are straight, just try not to be over-doing the freshman study hall like giving a 3.5 freshman 10 minutes and that sort of thing.
but anyway, with that backdrop - redshirt freshman favor 'the safe way' more than any other player, as best i can tell. its true their failing out matters extremely little, and that i mostly 0 them all like i do any other player. but you also get more return on those SH minutes than you would for any other player.