Harrier Dude
Living the dream
Of course as an 0-3, you will not be eligible to be a Platoon Commander and inexperienced to be the Company Commander. But I am sure they might find something for you to do at the Battalion level. Who know?
/end rant
I think this is what he was driving at. A Battalion Commander is going to pick his Company Commanders from his Platoon Commanders (or some other Battalions). If you don't have experience as a Platoon Commander, it'll be hard to get a Company Command. If you don't have experience as a Company Commander, it'll be hard/impossible to make Major, let alone higher.
This, or course, applies only to ground MOS type folks. Nobody expects pilots to get to their fleet squadron with any appreciable experience except flight school.
A better way of looking it that problem is to think of it like fleet acessions. Guys who get to the fleet as a nugget, but as senior Captains or new Majors. They may find themselves having their first fleet job as the OpsO or MO. Then again, they may not get those jobs at all because their CO doesn't think that they're ready, which gets them passed for LtCol.
Same problems.