Okay, here's a demonstration of the two relevant files.

Here's a gif. It's a little over 100kb, if you want to count.

Alright, cool. Now here's an mp4, converted using FFMPEG with the commands listed on your guide to making a superior image.

Now let's look at a webm using that same feature.

Do you see the problem here?

Yes, there are lossless ways of converting them. But given that bluesky is currently handling png compression very poorly, I don't think it's going to work how you think it will.

Does that answer your question?