I have never had a problem and I'm sure that I've trapped more than just a bit of 'moisture' inside the bead .
The only difference is water will take a bit longer to dissipate , but it does .
Just for something to think about : why do a lot of shops slop soapy water around a rim & tire when mounting ?
They keep a bottle and rim mop attached to the changing machine .
Anyway , like I said , I'll keep doing what presents no problems and works for me . ;)