That's not entirely accurate. Mostly, but not entirely.

"Profit" isn't how the ATF determines whether a private seller requires an FFL for their activities. Their, incredibly vague, definition is "engaged in the business" of selling firearms.

They don't care if someone buys a rifle and then sells it for a couple hundred bucks above what they paid. They care if it's done repeatedly.

From the number of guns on that guy's table, I would guess he is likely a licensed dealer.

The important part to note in the video is the abrupt cuts during the "sale." There was an adult with the kid, it's entirely possible their participation was edited out.

FFLs are prohibited from selling long guns to under 18 and handguns to under 21. By federal law. No state law overrides that restriction on FFLs.

Private sellers are largely bound by state laws regarding age restrictions, mostly pertaining to the legal age of possession in the state.

This was filmed in Virginia, which doesn't restrict private long gun sales by age. That's open to disagreement, of course, but kids have been shooting since they were 10 in rural states for a century.

This sale was either entirely legal, entirely legal and the video was edited to make it appear differently than it actually happened, or a felony that would result in loss of license and prison time for that dealer if he were reported.

Given the obvious bias against gun sales, I'm gonna guess "we shut down an illegal gun dealer" would have been the topic if this sale were anything even close to illegal.