Mar 2 2019
I've put in my todo list to make a bot for commons which identifies all the files with this problem. I'll try to get around to doing it before the summer.
I've had a look at the category https://commons.wikimedia.org/wiki/Category:Animated_GIF_files_exceeding_the_50_MP_limit 50MiPixels doesn't seem to be the limiting factor.
@Aklapper Why are you mentioning https://en.wikipedia.org/wiki/Unit_circle#/media/File:2pi-unrolled.gif ? - At 9.68 MiPixels that is totally irrelevant to this bug.
Nov 26 2018
@Aklapper from my point of view this and T25063 seems to refer to the same problem. This bug is however the stated reason in https://commons.wikimedia.org/wiki/Commons:Maximum_file_size for why you cannot upload large GIFs. If one is closed, the reference in commons should be updated to reflect this.
Apr 22 2018
I'm not totally sure how this is supposed to work, but it's my understanding that preview versions should automatically be generated, which they are not. Please have a look at the usage at https://en.wikipedia.org/wiki/Unit_circle the included file there is not animated at all. If this is working as intended the commons category probably needs to be removed.
There is actually an entire category of files affected by this bug: https://commons.wikimedia.org/wiki/Category:Animated_GIF_files_exceeding_the_50_MP_limit
This is still the bug which is associated with not being able to generate thumnails for larger Gifs. If this is resolved there exists another bug. See https://commons.wikimedia.org/wiki/File:Unitycircle-complex.gif for a recent example.