Applied display mode 1920x1080 on android TV while steaming 4k movie when using frame rate only matching

Hi,

i have a 4k google tv and i installed the stremio app internally (no streamer, just downloaded stremio directly to the TV).
i have frame rate only matching enabled in the settings, and sometimes when i watch a 4k movie i get a notication that says "Applied display mode 1920x1080@50hz", why does it say 1920x1080 when my TV is 4k and i am watching 4k content? is it because the notification only refers to the UI resolution but the video is playing at 4k?

just want to make sure that the video indeed plays at 4k and it doesn't downscale to 1080P or something like that...since i don't have any way to display statistics on my goolge tv, so i have no way to verify that (TCL C845 if it matters, anyone knows a way?)

Thanks!