The problem Youtube has is that it wants to make sure you can't skip the ad, so it has to signal in some way to its front end and app that this segment is an ad. That mechanism can and will be used to skip it with other clients. They can put the ads in band of the video stream like twitch does but if they are genuinely indistinguishable then they are also fast forward and skippable.
If they're injecting targeted ads in the stream, then the stream producer must be 'smart'. It's not much of a stretch for it to enforce playing out the segments at approximately realtime (or whatever speedup they want to allow), and to force the advert segments to play out before anything past them. Some sidechannel could be used to inform the client about what's going on and produce a sensible playhead position.
It seems inevitable that this is the end game, and I don't really see viable ways around it for realtime playback. For offline playback, yeah, presumably that sidechannel includes enough information to cut out the ads.
TYT has to mark the ad segment, they are required by law to do it. And no matter how they try to obfuscate it, their own webpage must be able to extract that info, and present it to user. So it is pointless to integrate ads if you are going to provide the timestamps to skip.
Just look how Facebook does it, there is no "Sponsored post" anywhere in HTML, the literally place entire alphabet multiple times, each letter in separate span/paragraph tag, and then use CSS to actually style that into a message of their choice. All of that work just to prevent simple adblocking rules to work.
