Not sure if it was you or someone, I had a discussion before and I think the job SecDef should not have any military experience at all, that post is (or was) supposed to be a civilian oversight of the miltiary, we are not a military junta, we don't need or require a military supervision of the military, if this is a civilian matter, then it only make sense if the head of that department was a civilian.
SecDef is about National Defence Policy, not necessarily the control and direct management of the Armed Forces. And this problem was highlighted when the UK promoted Penny Mordaunt to become Secretary of State for Defence when she achieve a rank of Sub-Lieutenant, and subsequently bumped her rank to a Captain (that's a 5 rank jump)
https://en.wikipedia.org/wiki/Penny_Mordaunt
That said, if you are completely alright with what Hagseth said last night, well.....