`@actions/cache`, why are paths needed to compute version

Describe the bug
When using the cache action, the path is used to generate a unique version.
Unfortunately depending on the runner type official or self-hosted) the workspace do changes and creates a different version.
This leads to a mistmatch and a failure.

To Reproduce
Steps to reproduce the behavior:

1. Have self-hosted AND github runners available
2. Create a workflow that cache some folders using ${{ github.workspace }}
3. Have multiple matrix start and restore the said cache
4. See failures on runs that are on a different type of runner than the one the cache was created on

Expected behavior
I do wonder why we actually care about the path at all when restoring?
If I did cache some folders, and I do want to restore them, shouldn't the cache key be enough to justify a proper cache match or miss?

Might be related: https://github.com/actions/toolkit/issues/1377

Start by reproducing the cache mismatch with self-hosted and GitHub-hosted runners, using ${{ github.workspace }} in a matrix workflow. Read the related issue in actions/toolkit#1377 and trace how @actions/cache computes its version. Done means establishing the intended role of paths and defining consistent cache restore behavior across runner types.