I had 2 laptops on last night, each connected to the same WiFi, each using more than 1 browser with an auto refresh extension and I never saw anything other than the holding page even after it was sold out, so that would suggest you're right.
BUT, my phone, on its own separate 4g connection, was also displaying the holding page well after half 6 so I don't think the theory holds up there.
Interestingly, I did notice that one of my browsers (opera) started to show 'event not found' eventually, but the other browsers on the same laptop still had the holding page. So perhaps each browser is seen as a separate session?? 🤷