After proposing a file size restriction related to $wgMaxAnimatedGifArea limit, I noticed animation when generating new thumbnail sizes. Previously cached image do not animate. This happens even when both input (2,000 × 1,600 × 50 frames = 160 mp) and output (1,600 × 1,280 × 50 frames = 102 mp) exceed the 100 mp limit scaling (tested on Interfering waves simulation.gif).
Documentation for the sibling property $wgMaxImageArea suggests VipsScaler ignores these limits, but only for PNG and JPEG.