Isn’t a full HD resolution ( 1920 x 1080 ) almost four times less pixels than 4K ( 3840 x 2160 )? I think I understand that a higher bit depth gives me more information per pixel, resulting in for instance less banding, but I still expected my 1080p 10-bit video files to look very soft and literally low-res.
If you’re on Windows, it is being upscaled unless you’ve manually gone in the settings and turned it off.
Even then, the TV itself could be upscaling it, too.