Andrew,
When you have CHECKED IN the objects in one machine it also updates the WORKSPACE on the server side (See pic). If you are using the same WORKSPACE name, and when you are using the 2nd machine, it SYNCs with your WORKSPACE (only UPLOADED/CHECKED IN objects) on the server side. Hence it does not show "out-of-date". You can verify by checking the VERSION.ITERATION to see if it matches the COMMONSPACE. If the object is in a different WORKSPACE, you will get the "out-of-date" warning.
I'm no guru and we don't practice using two machines because with Windchill, you don't know what to expect. This is what I think is happening to your situation 🙂
Calvin
[cid:image001.jpg@01CFAD66.BE23CB40]