That's an amazing idea. I'd love to see something similar implemented. I can't see any real downsides.
To answer your question, some preview exists, but not enough to really intrigue a reader if you ask me. It'd be nice to see them at least attempt a Substack-like model where writers can choose the placement of the paywall. On there, I've allowed people to read at least 50% of a piece before deciding, as opposed to Medium's roughly 10%.
It's true that the culture has changed quite a bit since 2020. But even just this week, i clicked on a website, got paywalled promptly, and made an immediate mental note not to revisit it.
Thanks for reading, Jeffrey! And sorry for the delayed reply.