You might see that the first time a user has ever logged on to a machine, the Firefox settings are not delivered as expected.

Or that some settings are present, yet others are not.

Some settings are stored in Firefox databases; and those databases aren’t created until Firefox is run the first time.
And, PolicyPak doesn’t / cannot pre-create those databases.
Items that may not show up first time include Pop-Ups entries and bookmark settings.

So, PolicyPak is delivering the settings, but then they are going no-where because those databases don’t exist until Firefox is run first time.

On the other hand, many other settings are stored in Firefox configuration files.

For simpler items, those files do exist (anytime Firefox is installed) and we are place some items in there, and have them appear, even at first use.

Which is why you can see seeing mixed results: Some settings appear a-ok first time, others not until Firefox is run two times.