And they'll still see a ton of YouTube ads.
I have a little-used gmail account that I registered a few years ago, as my original gmail became completely overrun with spam and I switched to Fastmail.
I added a credit card to the account and tried to pay for Youtube Premium and was immediately flagged for suspicious activity. To reactivate my account, Google wants me to verify my identity with photos of goverment ID and a full KYC-style form.
No thanks. I signed up for https://nebula.app/ instead - they were able to process my payment on the first attempt.
A potential problem they're trying to prevent might be where money launderers use google accounts to funnel YT Premium money to specific channels via watch time (since Premium pays out a lot more, and pay per minute watched[0]).
On Android you can simply install an alternate YT client, boom, job's done. Works on Android TV also.
On iOS, the content blocker lists in Safari can block YT ads, but there's no way to block them in Google's YouTube app unless you jailbreak and install a modified app. So just watch YT in Safari.