I actually used one as my gravity ATO for several years. I didn't use it behind any real pressure though, just gravity from a 10 gallon tank sitting just above the sump. I never had problems with it.
Yes. I use the flood guardian (aka “marriage saver”) to automate my rodi water production. Outlet turns on 2x a week that it is connected to fill my ato. I added an auto flush that flushes the membrane when it starts and every hr. One of the greatest additions I’ve made.