One thing about U/V is how do you know it does anything? Having no sick fish might just mean you are doing a good job in caring for them.
You could in theory, add fish with say ich to a tank with U/V. If you do this several times over a period of time, and the disease never spreads it might mean the U/V is working. When you read up on U/V the levels needed to really be effective are much much higher than what is typically used in a home aquarium.
As for Fish Tuberculosis (TB), and Neon Tetra Disease (NTD). They are different diseases, but share some similar symptoms. Bottom line is the result is the same. Fatal, and contageous. Best to euthanize the fish early. Though there are many thoughs on euthanizing fish, I personally use a pair of snips to sever the head at the spine, then put the fish in the trash (no flushing). It is quick, humane, and prevents contamination of local water supplies. Properly putting fish down, while not pleasant, is a responsibility we have to accept as fish keepers.