Giphy wasn't even GIF based. They were WEBP(?). The name comes from public perception: a short animated clip is a "gif", not a "two second video file with no audio track".
"Gif" as a word has been redefined to mean more than the file format.
GIF is just a concept here, but if you upload an animated .gif to just about any large image sharing platform, they will convert it to a video format and serve in a <video> element to save on bandwidth. I'm not sure who was the first to do this, perhaps imgur with their invention of ".gifv" url suffix? [1] However right-click -> save image as... on "gifs" ceased to be an option long ago.