Bookworm has the right input. An idling engine is still driving the propellor so any comparison of ROD with that of a stopped prop is meaningless. Try pulling the mixture to cut-off first.
Those saying that a stopped engine subsequently needs a very high IAS to send it over compression....have you not tried pulling 'G'? Pitching up changes the airflow through the propellor disc and improves the situation.
"My" Bulldog (XX623) went through a period when it occasionally stopped its prop in spins (can't remember which way the prop went now, far too long ago, but it occurred when the airframe tended to catch up with the prop in roll).
It would then need the starter button unless I pulled harder than for a normal "recovery from the descent", when it would go usually go over compression and restart itself.