We want to show a sample immediately as a user changes what they extract. On a static website, this is fairly easy. You simply run what the user created on the currently visible page.
However, when you involve interactivity, you can no longer do that. The major problem is idempotent operations. Imagine a click that changed the dom of a page. And now imagine running the sample on that same page. Re-running the sample may no longer work, because the click could have changed the page in such a way that the extraction no longer works (e.g. it deletes an element from the page).
To solve this issue, we actually reset a "hidden tab" to the starting state of the page you're on. This happens every time you re-run a sample. Unfortunately, it's not possible with Chrome to create such hidden tabs. We also mess with the cache to make sure that this tab can be reset really quickly, something that we couldn't find an API for with chrome.
Hope that answers your question.
Not sure if it does fit all your needs.