you are partially wrong.
in game development a skin technically speaking is the texture only. they replaced all the assets with more modern ones (textures, models, animations, sprites, etc), but kept the timings for the animations, so that all animations last equally long.
animations however are just visuals, triggers for damage etc follow the same timer, but animations dont trigger events, they are aligned with them - animations and triggers can also be misaligned, as it was the case with numerous units in wc3, for example the doomguard.
animations work with coordinates and time. time xy = position z. 3D animation, however, are not strictly bound 1:1 to time like a video, time is relative and animations have basically infinite resolution. if you take a video with 30 fps and slow it to 50% its running 15 fps, showing each picture twice as long. animations, however, if slowed by 50%, will gradually slow down but not stutter.
for example if a game runs animations with 60 fps (not game fps, they’re not coupled, not today that is) a set animation, e.g. reloading, is set to last 120 frames, it takes 2 seconds ingame time to reload. the animator now has 120 frames timestops to fit the animations into the 3D coordinate system. you set keyframes for the bones in your model to be at a specific place at frame X and the animations is being interpolated for the time between. if bone A is at 0/0 at frame 0 and at 10/10 at frame 10 its at 5/5 at frame 5 if the movement is linear. if you change the fps for the animation, the animation speeds up or slows down, as it lasts longer or shorter, its not smoother. its like comparing vector and 2D raster graphics. vectors can have a size attached, but can be scaled infinitely. rasters will pixel up when sized up.
its the game engine that chops down animation framerate for playback, its not the animation itself.
i tested it and the wc3 editor plays all animations with high framerate, while ingame wc3 plays all animations at low framerate. i would say editor runs full 60 fps animations, ingame 30 fps - or Hz for that matter. but its not just framerate, i guess the game actually skips frames in the animations.
if the real animation is based on 60fps the game cannot just run the animations in 30 fps, as the animations would speed up, right? so i think the game drops (ignores) frames to have 30 fps animations based on 60 fps animations and this causes jittering.
this is especially visible with the obisidian statue. its idle animation is a hovering animation, it just floats up and down. in the editor the obsidian statue floats very smoothly, ingame however the statue jumps noticably, its not a smooth transition. and this is true for both classic and reforged graphics.
so, why didnt they change it.
- lazy.
- game timer for syncing up whats happening on the map. i think its very possible the game runs on a 30hz tick rate that syncs everything that happens on the map on a 30hz basis, that means it would make sense to run the game animation on 30hz (30 fps) aswell so that each frame of each animation is linked to one server tick.
no2 however isnt set in stone - you can increase the tickrate, but you need to realign the timing for the game. and now we’re back to no1 - and this also increases server load. running a 60hz tickrate basically doubles the server load, doubles replay size, doubles compute load for that operation (but this works in sc2, so yea). considering how little they care for wc3, they probably didnt want to increase server load for this game to save money. also save money on the development side.
increasing the game tickrate would be a major quality of life upgrade for old and new graphics and would have been my no1. priority for an engine overhaul. they didnt do it, like they didnt do alot of other things. so thats how it is i guess.