The timing makes this the most obvious alternative when you find yourself getting ads again - they're hoping to capture the portion of adblock users that are unwilling or unaware that they can switch off of Chrome (or continue using uBlock on chrome for the time being if you ignore their warnings). To add insult to injury, it only stops "most ads".

I say this as a long time subscriber to YouTube Music + Premium. I want to support the people, services, or content I value - and doing so directly with money is much more appealing to me than doing so through ads. But when you ask for money and still show ads, I get a particularly bad taste in my mouth. (See Netflix and Hulu's half-ad-supported tiers)