I seriously doubt that tung oil will change the sound THAT much... while it undergoes a polymerizing reaction, the "strength" imparted seems to be minimal
it seems its been commonly stated (on DFO, amongst others) that you'd need to do 4 to 6 coats to have any real effect
as an experiment, i layered 3 sheets (about 2" x 3") of paper towel on top of each other, and soaked them in tung oil, tamped lightly to promote absorption and let them dry/cure for a month and a half
the three sheets adhered to each other, but i wouldn't call them strong by any means; as a quick test, i loaded up pennies on one side of the sheet, and reached 10 before they fell off
the same test using a wood hardener (PC Petrifier) reached 23 before there was not enough physical room left on the sheet to hold any more
I think tung oil IS beneficial as a sealer, though
I just need to get a matching set of new heads to hear what the SOUND differences are