This is the only real problem I have with how they handled the situation. But it's a big problem.
Whether or not these folks on free plans are ever going to convert to paid, they trusted PlanetScale to serve as a critical building block for their project/business. I think the least they could do is ease the transition by offering them a reasonable amount of time to offboard.
I personally would never trust critical infra to a company that has ever abruptly terminated a product offering with only 1 month notice.