FT6t2 Screen Resolution confusion

[Gerry Tool]

On first boot, I found my screen resolution at an all time high of
1920x1232 with refresh of 60Hz.

I used System > Preferences > Screen Resolution to set it to a more
comfortable 1600x1200 at 75Hz.

However, the login screen appears to still be at the original 1920x1232
at 60Hz, despite me checking the box "Make default for this
computer...".

I see that there is another System > Administration > Display menu item
which opens a different dialog offering a Resolution setting.  However,
this dialog only offers 800x600 and 640x480 and two color depths.

Why is the login screen still at the original resolution?  This has
never been the case before - it always tracked the setting I made in
Preferences.

Also, what is the purpose of the Display settings dialog vs the Screen
Resolution dialog?

Thanks.

Gerry