To the best of my knowledge, the Mercury Transmit feature only sends the timeline to your hardware "as is". It's up to the hardware to do any necessary conversion to make it work for the monitor.
Yep, that's what I figured. Kinda lame, considering the other two thirds of my post workflow, After Effects and Resolve, seem to handle this without a hitch.
Should have spent the extra $300 for the Decklink 4K, although I have a feeling I would still be in a similar situation, given that my monitor supports 2048x1080 and I'm working at 2048x854, not to mention that it leaves me high and dry if I need to work with 4k in Premiere.
The workaround would be to work in a 2048x1080 timeline, but since we're working with different flavors of resolution, 1080 Phantom and 2K, 4K and 5K Epic footage with all different kinds of resizing, reframing and cropping, I would need a 2.40 matte over the edit/finish timeline to have some sense of the actual framing and then either nesting the sequence in a 2048x854 sequence or copy and pasting the final piece from the 2048x1080 timeline to the 2048x854 timeline. Neither of these options is very appealing to me when I could just be working natively in 2048x854 and skip all of this, like I am with AE and Resolve.
I'm liking most of what Premiere is offering, but there are some details that make me think the people engineering this software don't actually use it. Like needing to have the Program monitor in focus for the "create still" key command to work or some key commands that should always work, regardless of what window is in focus, like toggling targeting. For some inexplicable reason, the "Show in Finder" command does not work in the timeline. It works in the project tab and "Show in Project" works in the timeline.
Anyway, off to the Adobe feature request/bug report site, which incidentally crashed my browser and lost my request the last time I tried to submit one.