I know it’s a small number and I don’t think it’s anything I want to watch, but an ad-free plan should not contain ads, ever, period. It’s the principle of the thing. Besides, if they’re willing to sign contracts that include ads even in the “ad-free” tier, there is nothing stopping them from doing it again in future.
Edit: actually, Grimm is one of the main reasons I would subscribe. so, yeah.