Bugzilla

Looked into this a bit more and as it stands, the current behaviour seems to be in order.(In reply to Julien Cristau [:jcristau] from comment #2)
> Sounds to me like auto updates weren't actually disabled here.  How did you do that?

This assessment might indeed be accurate. 
Looked into the report a bit more in depth but, there wouldn't be an issue to (/or that we can at least) reproduce at the current date.

- attempted to get in a range were users might not receive the update, but was unable as each one triggered the update(to 77.0.1 as for today) but no success;
- checked the restart -> update scenario with several builds such as 73.0, 69.0, 64.0 on macOS 10.15 / Windows 10, so it doesn't appear to be a regressed behaviour. 
As far as the about:[....] pages go, they appear to trigger the update after restart and to be consistent throughout the older builds as well; checked and confirmed for about:support, about:telemetry, about:credits, about:about, about:crashes;
- about:newtab appears to be indeed "excused" from the update as Robert mentioned;
- did some additional checks with turning off updates via user.js preffs: user_pref("app.update.enabled", false);  and user_pref("app.update.auto", false); and restarting the browser kept the builds from getting updated to the current version as expected.

Looked into this a bit more and as it stands, the current behaviour seems to be in order.

(In reply to Julien Cristau [:jcristau] from comment #2)
> Sounds to me like auto updates weren't actually disabled here.  How did you do that?

This assessment might indeed be accurate. 
Looked into the report a bit more in depth but, there wouldn't be an issue to (/or that we can at least) reproduce at the current date.

- attempted to get in a range were users might not receive the update, but was unable as each one triggered the update(to 77.0.1 as for today) but no success;
- checked the restart -> update scenario with several builds such as 73.0, 69.0, 64.0 on macOS 10.15 / Windows 10, so it doesn't appear to be a regressed behaviour. 
As far as the about:[....] pages go, they appear to trigger the update after restart and to be consistent throughout the older builds as well; checked and confirmed for about:support, about:telemetry, about:credits, about:about, about:crashes;
- about:newtab appears to be indeed "excused" from the update as Robert mentioned;
- did some additional checks with turning off updates via user.js preffs: user_pref("app.update.enabled", false);  and user_pref("app.update.auto", false); and restarting the browser kept the builds from getting updated to the current version as expected.