Retina Display's Screen Resolution Not Recognized Correctly

OS is High Sierra
PsychoPy version 2021.1.4 standalone
27" imac w/ retina display (5120x2880)

My hope is for PsychoPy to know the screen resolution of my imac retina display which is 5120 x 2880 pixels. I need to be able to draw lines to the screen that differ in width from one another by only a pixel, and I need to be able to get the click location of the mouse to the nearest pixel. Essentially, I need to be able to take advantage of the full resolution of the screen.

Hoowever, at present, PsychoPy treats my screen width as 2560 x 1440 (and does so no matter what monitor size I specifiy in the monitor center). When I draw a line 2560 pixels wide, the line fills the screen instead of taking half the screen. From what I have read, my understanding is this may be due to the way the retina display is treated, but I thought this had been corrected.

Any fixes to have the screen parsed at its actual resolution?
Any help would be hugely appreciated!