FWIW I upvoted you for contributing to the conversation but...
>1. This drone does not fit the description of any known DOD drone, so you should assume it’s classified.
I wouldn't. And I've held a secret clearance. Not fitting any "known" DoD drone means absolutely nothing.
>The DOD is meticulous about only flying classified aircraft in restricted airspace where they can prevent prying eyes and inadvertent attention.
Except for when they aren't.
>3. Classified and unclassified aircraft are not just operated by a dude that hops into a plane or sits down at a drone console. They’re planned out. They’re also not operated in a vacuum. If your scenario of a classified drone operating in this airspace were true, and the drone was picked up by a friendly chopper, the operator would most likely immediately land safely and have someone reach out to the pilots and let them know not to mess with the aircraft.
You can always spot a layman talking about this when they talk about things as "classified" or "unclassified". Classified what is the relevant question. Confidential? Secret? Top Secret? ???
>4. I consider it highly unlikely the DOD would ever use other agency resources to unwittingly run training Ops.
It's a good simulation of what a similarly advanced country might have on hand. The US, China, and Russia routinely conduct "response time" checks by putting a proverbial toe in each other's airspace to test response times and responses in general. The idea that they would never do it with American organizations is presumptuous. Our respective militaries pay close attention it when it happens but aren't particularly alarmed by it because it's not rare.