A second try loading each site in new tabs seemed to work, but this time each gave a different ID. One starting 3fa2, the other f918
Reloading each tab then gave two different numbers, 7eb6 and 6f83
Subsequent reloads did not change again.
Loading the sites in to two more tabs, gave yet a different pair of numbers (1934 and 1667), reloads of those tabs yeilded another pair (b308 and 3df8)
There was an initial screen, then a redirect to another page containing the text below, and appearing to depend upon JS being enabled.
"Waking up
To keep Glitch fast for everyone, inactive projects go to sleep and wake up on request."
That redirect is different for the two initial URLs, but is of the form:
where HASH is a sequence of hex characters, different for the two original URLs.I'm using Firefox, with uMatrix having scripts and css disabled by default, but 1st party cookies enabled.