Dry charcoal will absorb moisture up to what’s called EMC, Equilibrium Moisture Content. It does not hold nearly the amount of moisture that a dessicant or molecular sieve does by volume but it does absorb moisture. Don’t believe it? Take two pieces of charcoal out of a bag. Put one in a ziplock...
I think you have a legitimate concern. One thing you do not want to do is pull a vacuum (or reduced intake pressure). If I were to add something to the intake side I would definitely install a differential pressure gauge and make sure it was at zero while compressor ran.