Probably because it technically is - the program I use to make GIFs only has a resolution of a decaseconds, or 1/10th of a second, as opposed to milliseconds, or 1/1000th of a second.
As a result, it means I can't make GIFs play at 24 frame per second - the closest is 25 frames per second. As a consequence, the GIFs play slightly faster than they should, whereas the webm's and mp4's play at the correct speed.
Lord Aardvark
2016-04-14 22:05:06 +0000 UTC
The watermarked versions seem to be smoother & faster.