Which is the correct behavior because the test has failed – no human would wait 300 seconds, so timing out at that point and failing the test is reasonable behavior.
Here’s my diagnosis…
The page is waiting for something to arrive from the server. It never arrives.
You should try to find out what is hung up using the network tab in DevTools. Then, submit a report to the developers and explain their server is not responding in a timely manner.
Clicking the stop-loading button is not a valid means of completing a test case. Web pages should load in a timely manner and allow the test case to complete normally.