I assumed they worked because my plumber installed a magnetic one
inline to the new boiler I brought. I thought it was the same
principle. Are you guys all saying that these don't work either ?

I guess the word inhibitor rather than preventor is key. It only helps
but does not eliminate.

I've seen demonstrations where water particles run a different way
after going through this type of system. I am trying to prevent water
marks on the shower chome and glass only.