I think that as long as the AC supply to the heater is on the load side of the last pump disconnect you are OK. The purpose is just to prevent heat without pump power. There is also a flow switch in the heater but a belt and suspenders is not bad in this application.
When a timer is involved they want the pump to run a few minutes after the heat is shut down.
I am still not sure I understand all I know about this so I am open to correction.
