The point is that, while texture and data packs in general work with "all" versions (don't get me started on what's incorrect about that statement), the same exact pack may not itself work with all versions.
For example, a data pack may have a function which contains a /replaceitem command—prior to 1.17, this should work nicely. But the data pack won't work properly in 1.17+, because that command is deprecated; a separate .zip with the updated 1.17+ version (attached to the same submission) would be quite useful indeed.
That's just one of many examples that go to the need for such a change.