Provides versions clarification

Regarding provides, what is the role of the version? I've thought '>=0' means to accept any version available and having only one at a time in C-R, I've expected it would check and find one version and use it, regardless what is installed, so the installed package version would be replaced by the C-R available. But it seems it is actually bound to a version at build time so it throws things like this at upgrade time:

  ERROR    Error: failed computing upgrade: Failed solving solution for upgrade: Could not compute upgrade - couldn't uninstall candidates : could not satisfy the constraints: 
          twisted-libs-22.10.0-r1 and 
          deluge-apps-2.1.1-r3 and 
          !(deluge-apps-2.1.1-r3) or twisted-libs-22.10.0+1 and 
          !(twisted-libs-22.10.0+1) or !(twisted-libs-22.10.0+1) or !(twisted-libs-22.10.0-r1)

So, what is the point of specifying >=0 anyway if it can't use any version after all?

The issue names no files or tests; begin by tracing the provides version constraint and upgrade-solver behavior using the reported error. Document what >=0 means during builds and upgrades, and cover the described upgrade case so the expected behavior is clear.