Never heard of a 'pearl humidor' yet... maybe it's time? The silk thread pearls are strung on isn't likely to enjoy the treatment nearly as much as the pearls might. Vivat Nylon, I guess...
Can't say I know for sure that pearls NEED to be kept any less dry than the usual house. Caitlin, your experiment with the swampbox is the first evidence beyond lots and lots of hearsay. Thanks!
PS. About the mist... If I am reading this right, the pearls move from below 7C to over 20C. That sounds enough to get a bit of condensation on them from the air humidity in the room. Nothing else... IMO; it would be a disproportionately HUGE amount of moisture to come from the pearls themselves, even partially.