Customer Support told me to request a bug fix here

[BlakeMorrison]

"This is identified behaviour to do with compatibility between the Windows Operation system automatically applying a high DPI sc.aling to ArcGIS Pro resulting in the behaviour you saw previously. 

You can submit and idea on the Ideas website. 

https://community.esri.com/

I would highly recommend that you create an request so that this behaviour can be addressed in future releases."

I don't understand the message I got. But I'm passing it on. ArcGIS Pro doesn't maximise to the full size of my screen's resolution.

[SimonSchütte_ct]

You probably have issue with the DPI awareness on windows.
scaling - Is it possible to scale specific apps on Windows 10? - Super User

Windows Tip: DPI Awareness status definitions

Per-Monitor Aware:Per-monitor DPI-aware. These applications check for the DPI when they are started, and adjusts the scale factor whenever the DPI value changes. These applications are not automatically scaled by the system.

System Aware: System DPI-aware. These applications do not scale for DPI changes. They query for the DPI one time, and then use that value for the lifetime of the application. If the DPI changes, the application does not adjust to the new DPI value. It will be automatically scaled up or down by the system when the DPI changes from the system value.

Unaware:DPI-unaware. These applications do not scale for DPI changes. They are always assumed to have a scale factor of 100 percent (96 DPI). These applications are automatically scaled by the system at any other DPI settings.
Windows scaling issues for high-DPI devices - Microsoft Support

You can also scale within ArcGIS Pro: Set user interface options—ArcGIS Pro | Documentation

[BlakeMorrison]

My ArcPro window doesn't maximise to the full size of my screen resolution. I continuously click through/behind my ArcPro session because there appears to be a 1 pixel border around what should be a maximised window.

I can play with the scaling settings, which fixes the first issue but creates another issue, then I also lose any sort of anti-aliasing within ArcPro making it essentially visually so unappealing as to be unusable.

Tech support seems to have identified the issue as being a known incompatability with ArcPro software and Windows. I'm posting here to suggest that compatability should be strived for, especially  considering there is only one supported operating system.

[KoryKramer]

Hi @BlakeMorrison It sounds like you were trying to report a bug using ArcGIS Ideas. I apologize if that is the direction that you were given by Technical Support, but Ideas is not the place to submit issues that you feel are bugs. 

We followed up on this on our end and it looks like a new case has been created so that you can further troubleshoot the behavior you're seeing with Technical Support. If the investigation points to an issue that needs to be addressed by the software development team, support can submit that as a bug. 

Again, we apologize for any confusion in the guidance you were given, and are closing this idea as the issue will be handled through support.