It will still drain unless they caulked it shut, water is good at that. I've pulled enough of these out and found the small landfill in there, you could easily make it a non issue I guess.

However, any bike (especially dry weather bike) with cut outs in the BB shell is probably worth detailing monthly anyway isn't it? Every windowed BB shell I've found packed with dirt were from customers who abuse old racing bikes by commuting on them and never cleaning, fixing or installing nice parts on them etc.

The eternal quest for the maintenance free bike is Quixotic
e: i do not disagree with anyone in this thread