I'm pretty sure this will happen if your subscription lapses. The logo will keep the Premium badge because you're still technically subscribed, but your subscription is suspended so the perks are disabled. At least, that's the only time I've ever had this happen.
Ah, interesting. I'm curious what else you would pay for, though, if not for the removal of ads. Unless there's still Premium-exclusive content?Though I thought they stopped doing that a few years ago.