I'm not even sure that the assumption all wood exchanges moister is actually correct. Take the Mary Rose bows found underwater. I believe some have even been shot! Also finishing oil from liberon makes this claim "A most dramatic demonstration of the qualities of this finish was given by Jan Sanders who, having turned a small oak bowl, applied three coats of finishing oil, allowed it to dry and then poured a quantity of blue water based wood dye into the bowl. After gently swilling it around, Jan poured the dye out and wiped the bowl dry. Needless to say no trace of the dye could be detected on the inside of the bowl. This oil will give good resistance against water, alcohol and food acid marks and will give a matt to satin finish dependent upon the number of coats. A gloss can be achieved by applying a paste wax. Also approved safe for toys. Coverage: 1litre to 8 - 12mē. Drying: approximately 5 hours."
My feeling is that modern finishes DO seal a bow almost completely, if applied correctly. And I for one like this, if my canoe capsizes I want to know that my bow will be fine after a little dunk. Some of the new floor finishes are even more bomb proof!