There should be an asterisk beside one of the modes on the output of the second command next to the TV’s preferred mode.
Your TV is not reporting a native/preferred mode. Because of this we default to 720p.
This doesn’t stop you selecting 1080p in Kodi however, so it only affects the resolution of the boot screen.
The program that displays the boot screen does not do high quality scaling so any boot resolution besides 1080p will cause the word OSMC to look a bit jaggy.