As far as I can establish by quickly examining the script, yes. The script downloads a base Ubuntu version from:
$ubuntu_version are the Ubuntu arch and version specified/needed.
However, it then modifies bits, presumably to make it work on Chromebooks. This seems to include settings for the touchpad, setting up software repos (mainly those used in standard Ubuntu), and making a patched kernel (using this amongst other things), as well as flashing new firmware.
So parts like the kernel and hardware/driver configuration may not be the same as in the 'standard' Ubuntu versions, but are necessary to make it work on Chrombooks. The software (desktop, applications & programs etc) used should for the most part be exactly the same as available in
standard Ubuntu installs as I think is uses the normal repositories.