You don't have to use the same image for the feature as the embed preview. The featured image is often the default (and you have a fallback just in case), but you can also choose to replace it for socials. Don't know what this is built in (on mobile) but it could just be using a different file.
I haven't seen this before so grain of salt but I'm assuming it's just to be eye-catching so you click to their site. I'm also assuming you wouldn't want it to be a gif on your own site because of accessibility concerns, but that depends on your requirements which vary pretty widely by country.
You don't have to use the same image for the feature as the embed preview. The featured image is often the default (and you have a fallback just in case), but you can also choose to replace it for socials. Don't know what this is built in (on mobile) but it could just be using a different file.
I haven't seen this before so grain of salt but I'm assuming it's just to be eye-catching so you click to their site. I'm also assuming you wouldn't want it to be a gif on your own site because of accessibility concerns, but that depends on your requirements which vary pretty widely by country.