This applies to some specialised weapon training courses too. Like course commander is a MWO or DXO but he is filling a typically CPT or MAJ post.
Never heard of combat side, actually. The closest is logistics, but they're very rear-echelon & I dunno what their COC is like. DXOs are supposed to be only part of MINDEF strength & not the SAF's. But the rest of what you said is true.
BTW To all, one don't "convert" to officer, one gets "commissioned". Neither do we practice the Commissioned Warrant Officer system, rather, we appoint them. Hence, in some cases, to commandent level.
"Tiger" Hong Seng Mak retired as a CPT, as did the other famous one, Shamsuddin. But I'm not sure if the old WOSE corps could get promoted like that. Then again, they were also before my time.