I think this is more of a complement to Selenium, where you can use Selenium to drive the browser to test the UI, with Polly providing recorded back-end responses. I need to look into it more, but this might address a need we have to make it easy (and quick) for our front-end developers to run our test suite locally during development, without having to spin up anything in the backend or rely on flaky non-Production environments.

EDIT: I am aware there are many other tools that can address this, we just haven't had the time yet to implement them. :)