Why a series diode for the mosfets in this circuit?
The MOSFETs have very slow (circa 1 us reverse recovery) bulk diodes so putting a schottky diode (65PQ015) in series with the drain stops the slow reverse recovery playing a role but, you do need diodes so the MUR1560s do this job and they have a reverse recovery of 60 ns. It's probably all about getting a few percent more efficiency from the half bridge when it drives the load induction coil.