I freeze excess coffee, too, always wondered, hmmm, why no freezer burn? A search on the almighty googlenator reveals a few mentions of it here and there, but nothing scientific . If you put tape over the valve bag or don't vac seal, there's going to be some ambient humidity in the container, and vapor pressure will cause a small amount of the water vapor to freeze, promoting further growth of ice crystals...

The concern here is, once you take it out of the fridge, the water crystals melt.

Wait.. automatic RDT?

Likely the response is that there isn't enough humidity inside the vessel to promote sufficient ice crystal growth, hence air-tight seal or tape over valve. Maybe a better question, under what circumstances would one get freezer burn with coffee beans, and thus, learn how to avoid it.

From another thread: Better Espresso thru Freezing

another_jim wrote:Given that roasted beans have no free water, they are probably not harder than room temperature beans. It may also mean they can be frozen and refrozen with relative impunity.

The problem of getting condensation on the grinder when grinding frozen beans is obviated because ground coffee will fairly rapidly absorb about 5% of their dry weigh in moisture. This may mean any condensate on the beans is absorbed by the ground coffee, rather than rusting the burrs.