Thats why on boiler set ups, I make it so both can run at the same time. Saves money on oil.
Thats a nice feature, I have a furnace, so I dont have that option. It's either one or the other, im guessing it has to to with head pressure? not being able to remove the heat from the heat pump?
I wasnt 100% sure the OP had a boiler, but I think I would modify my drawing a bit, and install a two stage t-stat to kick the boiler on only when necessary, and still keep the heat pump running... fun part of drawing diagrams.