The resonance appears much stronger when he Obliviates the Dark Lord Tom than later during the Transfiguration. Of course the former could just be stronger magic, but I assumed the alteration to V had reduced it (and thus he couldn't have started with the Transfiguration in the hope of getting a more experience entity to do the mind-alteration later). This would support the theory that V updated his old Horcruxes somehow, or just didn't connect them to the network. (There could still be variant Tom Riddles coming some years later!)