How can I export or share video that Photos app (on my Mac) made about one Person from my Gallery?

The only way I've found to save a copy of that Peoples presentation is to use the Screenshot app in the Applications/Utilities folder to record as follows:

1 - start playing and then pause the slideshow. Click on the gear button and set the type of music and length of presentation. Then move the slider back to the start of the slideshow.

2 - launch Screenshot app and click on the Record Selection button. And under options select where you want to save the movie.

3 - click on the Play button to start the presentation and when finished click on the Stop Recording button in the menu bar:

The resulting file can get rather large. A 29 second test movie I made came in at 167MB.