Yeah, I see that with the lower pitch gears but 48p is TINY and dust can be bad for the plastic...maybe they've found the lower pitch works fine so decided to save money. Companies often do not provide the best because it'd cost too much and that probably works "well enough" especially with the lower pitch they seem to all have....
I think it really depends on what you are running. If you've got a mega with the 48p plastic spur gear I'd err towards safe and seal it. If you have all metal mod1 gears I'd suspect it wouldn't matter if it were entirely exposed. Not 100% sure on metal 48p gears as those teeth are small and all it'd take is a small pebble or large grain of sand to possibly break a gear off...
I think it really depends on what you are running. If you've got a mega with the 48p plastic spur gear I'd err towards safe and seal it. If you have all metal mod1 gears I'd suspect it wouldn't matter if it were entirely exposed. Not 100% sure on metal 48p gears as those teeth are small and all it'd take is a small pebble or large grain of sand to possibly break a gear off...