So, looking further into this, I think an issue I'm running into is that the TV is an older type that can do 4k at 60Hz, but it does it at 4:2:0 chroma while using an older HDMI 1.4b chip. This lets it get 4k60 over the older tech, but at a lower chroma sampling.
Supposedly the intel chips will support this as well, but via a driver patch that was added back in 2017.. However, it appears that it's not being detected properly and this is causing some issues with (initially) getting 4k60 to show up on my resolution list.
Spent a few hours digging around xrandr and xorg code, but there's no good way I can tell to force the driver into 4:2:0 chroma mode.