Actually yes, Shell offers a subscription model that gets you a discount on fuel prices (you get the "premium" V-Power at the cost of "standard" Super fuel), at least in Germany - it's called the "V-Power Smart Deal".
...Okay, and the same is true of Tesla. You don't need a monthly subscription, you can pay as you go; the optional subscription gives you discounted pricing. It's just a loyalty scheme.
So no, they don't require a subscription to fuel up. It's just a loyalty scheme.