It's more likely how the cases were positioned in the course of things. If you have the case mouth tipped up a bit and there is enough water involved it's reasonable to think that one hour won't be enough time to evaporate the water as instead of just drying the surface off there are large droplets.I know after tumbling they go In a dehydrator for a hour or so. Then cool while In the dehydrator back to room temperature… maybe from going outside being warmer to inside in a cool house caused condensation to build up.
What I do is when my brass is done tumbling and separated from the media, I get a towel and put the brass on it then wrap it up like a hobo bag. I then bounce it all around to dislodge anything stubborn including water left inside the cases or even any media that I might have missed. It doesn't take long at all to be effective.