A very interesting discovery, Terry!
I used a different approach and checked the 12 POIs I most recently posted photos to. The result is 50:50, i.e. six listings had a video on position 2, they other six had none.
This does not apply to 360° photos, they appeared down in the list among all other photos.
For now, it confirms your theory @TerryPG 
I’ll keep watching.
Update for one exception now:
A listing with more than 1,000 photos, ironically shows the only video at the second but last position of the list of all photos. Looking at the Video tab, I do see four videos, including the one, I found a the end of the All list.