That assumption is right. But until now it was always compensated, so that in the mean it would be ~50hz. This correction mechanism apparently isn't enough anymore for the current fluctuations in europe.
7 karma · joined March 14, 2012
While this is also possible with SVG animations, they tend to be not as widely supported as CSS animations and at least I need to google for information about this topic as SVG is not an everyday topic for me.
Regarding GIF animations: they are larger in size and you first have to find and use tools to generate them. When avoiding the additional request: data URLs are ugly.