I admit I'm going into this with almost zero knowledge, so someone please point out if I'm being a complete tard. But, from what I gather, wouldn't it be really hard to tell if a child was viewing something that the uploader classified as not for a child? The only way I'd think you'd be able to tell is if the viewer was watching with an account containing an accurate birthdate. If a kid is just using the account of a logged in parent to search for Pokemon playthroughs and they stumble on Phil, YouTube isn't going to know it was a kid watching and not the parent. There's also the case of kids just making a new account with an older birthdate to get around things. I could see especially young kids not knowing this is an option, but I'd be surprised if anyone over like, the age of 10 didn't know better. And while Phil isn't exactly bringing in a mature audience, I don't think he's really hitting it big with an audience young enough to be effected by this. Hell, Phil's channel in general isn't exactly a goldmine for views. If I had to wager a guess, most of the views are coming either from detractors who need to mine content for videos, or legit fans who actually want to watch him for some wild reason. In the first case, I doubt kids are making detractor content/even know who Phil is, and for the later, we're dealing more with disabled adults than actual children.
It might make it harder for Phil to get ads if his stuff is flagged as mature or adult only or whatever, but with how few views he gets I can't imagine it would have that much of an impact. Maybe a few hundred dollars, which seems like a lot, but compared to the Twitch/donations which make up the bulk of Phil's payments, it isn't that bad overall. Probably still enough to get under Phil's skin and lead to more rants about how dumb YouTube is, but Phil does those whether or not YouTube is actually doing anything or not.
The reason YouTube got in so much trouble is that they were selling ad space to advertisers directly saying they could put those ads in front of children and they were using account data gathered to target specific ads to these accounts that they completely fucked all plausible deniability of them not knowing these accounts belonged to children.
They used to ignore this law by saying 'Wink Wink there is no one under 13 on our site because our TOS says you have to be 13 and over to create an account'.
In response to this the FTC is cracking down on YouTube, but YouTube worked out a deal with them to put the onus on channel owners whether or not to turn off targeted ads.
The FTC has made such statements as "the audience will be
presumed to be 12 and under", so even in the case of say an unboxing video of a $300 collectable statue of Sagat, because it is a 'toy unboxing', the FTC will presume the audience does consist a children 12 & under i.e. "for kids". If you make edgy videos using puppets or animation, because those are 'puppet shows' or 'cartoons', the FTC will presume the audience does consist of children.
The FTC has said they already 'have ways to go through the 23 million channels' and it's certainly not going to be with a fine tooth comb.
I'm starting to ramble, but to answer your questions: The FTC isn't going to look at accounts watching to make a determination, they are going to categorize videos and presume the audience contains children. . .because YouTube massivly fucked-up and flushed their 'Wink Wink Nudge Nudge Those aren't children because they said they weren't' deniability down the toilet.
It doesn't matter who your audience actually consists of, and it doesn't matter what your intended audience was, it matters whether the FTC will presume your audience consists of children based on an extremely shallow overview of your content. It also doesn't matter if you have restricted your videos as "mature content", it only matters what the FTC presumes and whether you have turned targeted ads off or not under the misleading label of "for kids" or "not for kids".
I'm just going to wait and watch and get a few chuckles from the sidelines hopefully. The more people try to spell this out for Phil, the more stubbornly he will refuse to listen. No one can navigate this correctly for him, and if he gets bit in the ass by this it will be hilarious.