We recently has this discussion regarding command line programs.
If you load either onboot you notice that there is no menu to launch them either.
This is because the extension maker has chosen to set them up this way.
If the maker had an included a freedesktop item for at least a menu then there would be a menu item (onboot) and
ondemand would work as it does for extensions with such.
The recent discussion conclued with support of cliorx, e.g., Exec=cliorx nano
That way ondemand programs could be launched with or without X.
The most recent release even supports freedesktop item without the X-FullPathIcon as well as using base generic icons!
The infrastructure is there to support it. It requires extension makers to deploy it.
Without a freedesktop menu item, ondemand works exactly the same way as onboot, i.e., only loads the extension.
One is then required to open an xterm to launch.