Hi ,
You can apply phasing groups to videos, but this won't show the phasing timeline in the video. Instead, the phasing group will apply to the video, so that the phasing timeline will be traversed by the video. In your example, each 1/3rd section of the video length will cover each phase.
To make edits to the phasing timeline, you will need to return to the phasing group settings.
You can view more details in our documentation covering Phasing.
Best,
Raghib