1080p/1080i impacts boot screen

[skizzo]

So maybe this will help someone else out. I was recently wondering why I sometimes was getting a boot screen to display and other times I did not. I was using the same OS version, same GPU, same resolution (or so I thought I was)

Due to using ResXtreme I did not immediately notice I was accidently switching between 1080p and 1080i resolutions. All the variables look the same across the columns for those two settings. It is much more obvious under the standard Display panel in System Settings.

Once I realized I was actually changing resolutions I figured out I needed 1080i in order for the boot screen/boot picker to work.

Besides just sharing as an FYI I am wondering if anyone can explain why the boot screen works under 1080i but not 1080p? Is that normal or do I perhaps have an exception happening due to using a mini display port to HDMI adapter? I am using these
https://www.amazon.com/gp/product/B077J8655R/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B005BZG8G4/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

The Mac Pro I am using for this is the 2nd cMP in my sig with the ATI HD5770. My "monitor" is a Samsung 48" FHD (1920x1080) TV (UN48J5000)