This is true for both the python and xml api

If you go to a url such as http://jenkins:8080/job/jobname/label=node1/565/ and get its api by adding 'api/python', you will get the status of that node for that build number

If the node is queued, then the api will reference the previous builds status

This also manifests itself in the ui, if a node is busy, the icon will be a dimmed color, and if you click on it, you will go to a page for the previous build