Just my opinion. I'm not a Veteran.
There are times to have the Service Rifle with a loaded mag and empty chamber.
And there are times to have the chamber loaded.
If circumstances dictate the Rifleman having a round in the chamber of the rifle,it would seem appropriate to have a round in the chamber of anyone depending on the pistol.
Whether that is an SOP or the person in command ordering "Clear chambers and load up in the trucks" or "Lock and load" before heading for an action.
IMO,the small unit commander needs to make that call while close to the situation.
I would not leave it up to the individual Snuffy to decide,but if a Squad Leader is about to cross the line of departure,it might be time to order "Load"
I can see no reason why that would not apply to those carrying a handgun.
Same with "Clear"