you can beg to differ all you want, and I assure you I know the difference between a heat only and a system boiler, OP has a heat only boiler, look at page 37 diagram 2:23 the wiring diagram for Y plan with this boiler, you will clearly see there is NO pump over run and the pump live is a switched live from the mid position valveI beg to differ, but only slightly. The circulating pump is [edit: should be]wired directly from the boiler.
[edit 2: there is confusion in the title; a heat only boiler is not a system boiler, and vice-versa]
https://idealheating.com/uploads/documents/logic-heat-h-installation-and-servicing.pdf