Screen resolution is lower than requested

[bcotton]

This is a cool solution, and matches my use case perfectly.

Some specifics:
2018 MacBook Pro 13" 16GB
BigSur 11.6
Most recent version of FluffyDisplay

I have a 5K iMac, so I request the display size to match, 5120x2880, however from the iMac side I only see a screen resolution of 2560x1440. I can confirm this on the MacBook displays control panel when I option-click the "scaled" button.

The about this mac -> displays shows 5120x2880. Strange

Any ideas?