There are "bad" coaches out there. Not just ineffective ones, but tyrannical ones, explosive tempers, unfair ones, coaches who play favorites so that it's impossible to earn PT once you get "in the doghouse." HS players have either met coaches like this or heard about them from friends. It's natural for them to try to spot them based on the limited information they have.
Playing time is only one of the things they'll think about, but I suspect it serves as a gauge for lots of other things too. If a HS kid watches a team for a season, does she see freshmen getting real chances to play? For example, Dawn made a point of playing a long rotation most of last season. This season, Kitts took a chance and came early and is now getting substantial playing time, and not just because of injuries. And Fulwiley has gotten playing time even though the guard spot at SC is already loaded. These have to be positive indicators for potential recruits.
And even injury-based opportunities mean something. It must be clear that Geno sorted through his freshmen and decided to give KK and Ash starting spots, and their performance showed he'd made a careful assessment. It's should also be clear that he's working on a slightly slower schedule with Ice and Q, but his intention is clear. This has to say to a recruit that he makes judgments based on performance, not favoritism or temper.