Display vs Device resolution mismatch

[DeNo 64]

Setting Steam Deck resolution to 3840x2160@30 results in display being set to 4096x2160@30. Meaning I have black boarders on left and right. Setting Steam Deck to 3840x2160@25|24 results in display correctly matching the 3840x2160 resolution and frame rate, and no bars. This is on both Desktop Mode and Game Mode.

Cannot set to 4096x2160@ANYTHING in Steam Deck Game Mode. This will default it back to 1920x1080@120. Desktop Mode I can. Although image is visibly squished on the 16:9 C9 display.

Was able to recreate the behavior on a windows laptop by setting to 4096x2160, then back to 3840x2160. Although on windows changing the refresh rate fixed the issue. Making the display output a 3840x2160 resolution.

Step up:
Steam Deck Stable 3.4.8
Anker 7in1 Hub (A8346)
Hdmi 2.0b cable
LG C9 (firmware: 4.80.03)