My 2 cents.
I do sanitize my system once a year. Why not it is minimal cost not labor intensive and does not hurt anything.
We do use a blue filter on the hose that is replaced at the same time I sanitize the system.
We use the blue filter primarily for taste of the water.
I do taste the water before adding it to the fresh water tank. Even with a blue filter some water just tastes bad.
IMHO if YOU are concerned about traces of bacteria, lead, pesticides, nitrates or high concentrations of chlorine in your water then get a First Alert WT1 Drinking Water Quality Test Kit or similar and test the water BEFORE you hookup to your RV or add it to your RV tank.