For whatever reason, pref("app.update.auto", false); does not get set (to 'false').this did NOT work
No idea why not?
The other two do get set as expected.
And that does help, somewhat.
With the two that do get set, I believe that it will at least stop "automatic" updates.
It should also limit 'Help | About', in that that alone will not cause an update.
Where it fails, by not having pref("app.update.auto", false); set, is in Help | About, if you actually click the 'Check For Updates' button, it not only checks, but will actually update you.
If you do have, pref("app.update.auto", false); (which autoconfig.js is not setting, for whatever reason), then Help | About -> Check will report an update is available, but not actually effect the update until you click that button again.
So in one mode it updates, automatically.
In the other, it reports an update is available, but does not automatically do anything.
So it gives you an avenue to see but not act.
And all this aside, as far as why an update may or may not occur, why an update may happen unexpectedly, at unexpected times, have a gander at some of the stuff I wrote, link in the dslreports link.