How Maze and UsabilityHub sync with Figma prototypes?

I’m trying to build a user research tool, kind of similar to Maze and UsabilityHub.
Basically, I want to give tasks to users, with a start page and an end page.
I tweaked around with Figma iframe embed prototype but the URL doesn’t change and I didn’t manage to find the relevant data points in the iframe code.

Do you have any idea how this service achieve a “Task done” screen when users land on a specific figma prototype page?