I'm pissed!

The medusa's holes haven't been a problem for me (running the 50mm 4800kv motor on 3s....). Brushed motors have open endbells, and vents in the cans. They hold up just fine offroad, and if anything, they have more potential to get screwed up because the windings are moving at high angular velocities, so any incoming debris can get smacked by the arm, and possibly sever a winding. Let's also not forget about the commutator and brushes...

The open endbell isn't a big deal unless you have a habit of running through iron filings.

Of course, if it bothers you, cover up the holes like others are doing. Problem solved.