Interactive video: VO focus stays on page in background while in full screen

Reproduce:
1) Open examples from H5P webpage in Safari on Mac
2) Navigate to interactive video component

3) Turn on VoiveOver (command + F5)
4) Use keyboard navigation to focus on the interactive video frame (control + option + arrow keys)
5) Enter the frame (control + option + shift + down arrow)
6) Change video to full screen
7) Try continuing to use arrow-based keyboard navigation to access video controls
8) Try using shift-based keyboard navigation to access video controls

Expected: When a video display is changed to full screen, the keyboard focus moves with it and is now on the video controls at the bottom of the screen. While in full screen mode, keyboard navigation is locked to the video and and video controls

Actual: When entering full screen, attempting to continue using arrow navigation (control + option + arrow keys) has no effect, and can't reach any of the video controls. Using shift controls instead still doesn't access video controls, but instead focuses on the buttons of the page in the background