The thing it really causes is using more materials, and more draw calls.
So it's not so much a desktop/laptop vs mobile thing as much as it is a scaling thing and a "rendering backend" thing.
Though you do hit the limit faster with lower-end mobile, just as you would with low-end desktop.
The more skeletons/characters your game has mix and match, the more important it is to repack. If most of them share the same base skeleton data, the more the caching change above will be a huge improvement.
And the more individual skeletons can share your repacked skin, the more benefit you get out of it.
And if multiple materials causes you to not be able to do certain things with rendering, or when it causes visual glitches, then it's also important to repack.
If you see no visual glitches or aren't doing any single-material-specific things, it shouldn't be a problem. Just add a Sorting Group component to your Spine GameObject if your Unity version is new enough.