His team are already backtracking his remarks with “What the PM meant was…”. From BBC:
“After PMQs, Burnham's team was at pains to stress his commitment that "national security is the most important duty of any government", and stressed the prime minister had been "consistent about getting the welfare bill down".”
Add to this I’ve just seen about the plans to practice calling up the strategic reserve from next year. That’ll include DH, he left nearly 7 years ago (just before Covid) but he’s on the list for at least 10 years, potentially for life as an ex-officer.