You are correct, the worst is RO water that strips all the goodies out
filtered water still has some goods and bugs in it, but if in doubt(summertime)
add 20% normal unfiltered water to your clean stuff
Use your cheapo TDM meter to test every month
so to spy on your water companies policy? ..lol
all this really means is you will be adding Epsom Salts or CalMag earlier than you normally would