Policies in Patch Management 7.5 are inconsistent with Windows Update.

We're running 7.5 and I have noticed that we have policies created in Patch Management that reflect various M$ updates. However, when I go to a machine that shows no software updates,In Altiris, I can run Windows Updates against that machine, and it'll come up with updates that are reflected in those policies.

Q: Why would windows update think a patch needs to be applied when Altiris doesn't?

Thanks