Teflon tape actually seals the threads from leaking by being crashed within the threads and being squeezed into the gaps and imperfections in the thread to thread contact between the tank threads and the plug threads. This keeps the water from working it's way through the thread spirals and leaking from the threads.
Teflon tape does not stop contact between the threads since it is crushed and squeezed into the imperfections. Otherwise if Teflon tape was so great at breaking the "electrical contact" between the tank
threads and plug threads the tape would still be intact when removing the plug and not crushed into spiral shaped remnants requiring removal before applying new tape.
