There are four large .gif files. I believe the one you are referring to is 2.6 MB and named `Duo_540X540_TransparentBG_3s_splitscreen_05.gif`, with a split screen comparison of what it would look like at 30kbps. The overhead is the graphics of the "montage", I figure.

I don't think the codec uses 30kbps by default, that specific example is showing what it would look like at 30kbps. Obviously if you have the speed for it, it'll probably raise the bitrate more. Duo is known for adaptively scaling up and down and smoothly switching between different network conditions.

If it's stupid but it works, it's still stupid.

I think their blogs are still based off Blogger which hasn't been updated in quite some time. (which they own so they could fix themsleves..)

There are only two ways of realistically demonstrating encoding artifacts: decode the actual format client side or transmit a lossless encoding. GIF surely isn't lossless, but its losses are somewhat orthogonal to those of the encodings in question. Still, yet could have done with much less of the same.