From the Clerky site it looked more like you pay for specific things and there wasn't some kind of overall monthly subscription dashboard (though I may well be wrong here), and for whatever reason my mind categorized those two things differently.

Though in saying that, Stripe Atlas is also just a one time fee.

So I think it's just a framing thing. The other ones called their things "products" and launched them as products, and maybe Clerky has done that too and I haven't seen it, but currently I associate Clerky more as a legal services thing.

Hopefully the insight into the (weird and non rationally justifiable) ways my brain is thinking about the distinction is useful