Yeah, but the Starter Plan starts charging an additional fee after $1MM (yearly? total?) revenue. So it's not grandfathering in at all, we just get shunted to the temporarily-free plan that everyone else has to start on.
Edit: Since my posting this Stripe has clarified that existing customers get the Starter package at no further cost, we we are grandfathered in.
(PM from Stripe) If you're an existing user of Stripe Subscriptions, you get Stripe Billing features included in your current price. (To be clear, there's no extra fees for existing users.)
Edit: Since my posting this Stripe has clarified that existing customers get the Starter package at no further cost, we we are grandfathered in.