>> YouTube accounted for 8.5% of total TV viewing in May, while Netflix was a close second at 7.9%.

Assuming that's true, I still don't think it matters that much.

I expect that a very large proportion of Netflix that's watched is watched on a smart TV. Much larger than the proportion of Youtube that's watched on a TV.

Interesting! Almost all my video watching is on a roku box attached to my TV. I may watch a tiny bit more Youtube than Netflix on my PC or phone, just because people send me links that way, but if the videos they link me are more than a minute or two, usually I'm saving them to "watch later" and catching them on the TV box.

I'd have assumed most people's proportions were similar and that therefore the proportions for the two services were similar; that is to say, for people who use both kinds of devices to watch video, I wouldn't have expected a big difference based on the specific service.

Do you have a source that suggests that people who use both kinds of devices watch a larger proportion of Netflix on the TV but a larger proportion of Youtube on PC?

This article isn't about streaming activity in general, it's about the Nielsen ratings, which as far as I can tell wouldn't include views on creators like MrBeast, just proper 'television'.