Check it with `youtube-dl -F`, a 8K stream is available, but may not be presented to you in the browser UI:

    format code  extension  resolution note
    272          webm       7680x4320  4320p60 32524k , vp9, 60fps, video only, 850.48MiB

If you want, you can download it for yourself like this (the +251 part adds an opus @160k audio stream):

  youtube-dl -f 272+251 https://www.youtube.com/watch\?v\=1La4QzGeaaQ

Incidentally some videos also have VERY low bitrate encodes that also aren't shown to most users by default. This particular video goes down to 256x144, but sometimes you see even smaller, particularly with a reduced framerate.