No, the video uses the image as a "poster" (still image placeholder when the video isn't playing) in that attribute of it.
Then it actually gives the source of the video to play in the tag within the tag.
The "on the fly" transcoding on the server side to webp is something some platforms do. the server-side is a jpg, but you are being served a webp with the appropriate content-type server header.
Pretty much all of that is done server-side, not your front-end side.
Thanks. I wrote it a bit iffy, but that's essentially what I meant, yeah.
I guess the only question left is why I can play the vids and get an MP4 vid while others can't play the vid and get x-mpegurl?
(or is that another implied and obvious answer? Last question, I swear, then I'll drop it. Just curious)
Discussion in the ATmosphere