I was curious about this and it is true only if you have an unlimited plus plan.

https://support.google.com/fi/answer/12999259?hl=en

This is news to me and I don't think this is true... or it's maybe hidden away somewhere. I am a Fi subscriber using a Google Pixel phone but YouTube premium is still $13.99/month.

Unlimited Plus (the plan with free YouTube Premium) is a dollar more per month than just buying the Unlimited plan and YT Premium separately. You also only get it free for a year.

is it? I've had fi for years and never noticed. I also don't watch much yt so it's not something I'm apt to notice I suppose.