PSVR Not Passing Through 4k (Unrelated to HDR)

I have an LG 27UD58, which is not an HDR monitor. I've confirmed that both HDMI cables definitely work in 4k by connecting them directly to the PS4/TV.

The issue is, when going through the PS VR breakout box, I can only get 1080P.

Has anyone else had this issue? Any thoughts/recommendations? Thanks in advance.