Currently the windows beta is a sequential operation. At the end of the sequential operation, the metadata used by the application to know the state of your machine is updated.
When you launch a sync on Windows, a new process is spawned to avoid blocking the UI during the sync step. This of course exposes an possible flaw in which the user (in this case you) kills the application leaving the sync process in an unknown step and not updated metadata. To avoid this case, the windows port kills all the process that are ran by the application except those that are performing a sync with the server.
What you are experiencing is the sync process working until it finishes. This is a feature added to the beta because we(it was me actually) considered that it was worse to have a corrupted sync in which you data could be removed than to use extra CPU until the sync is done.
This will remove as soon as we have a continues sync in the application in which the metadata will keep synced in a much smarter way.