I had a look too. In the UI movies are exported, not saved, and there doesn’t seem to be an export command in the dictionary.
You may experiment using the movie file formats as they appear in the export command (“MP4”, “MOV”).
save reference ¬
in file ¬
as saveable file format
I was able to create a movie file and save it, but couldn’t make it play.
use AppleScript version "2.4" -- Yosemite (10.10) or later
use scripting additions
set movieFile to choose file name with prompt ¬
"Enter file Name" default name ¬
"movieFile.MP4" default location path to desktop
set openFile to open for access movieFile with write permission
on error errMsg number errNum
close access myFile
set openFile to open for access myFile with write permission
close access openFile
tell application "Microsoft PowerPoint"
save active presentation ¬
in movieFile ¬