Excel refresh and PowerPivot refresh

We're using SharePoint 2013 SP1 and developing dashboards in Excel 2010 with 2012 PowerPivot for Excel. This means that interactive refresh (e.g. refresh on open) is NOT supported according to: http://ift.tt/1FRu6cI for PowerPivot. So far so good.

However refresh on open works fine for refresh of external data in e.g. an OLAP cube using excel refresh and not PowerPivot. However when we have both a PowerPivot connection and an Excel connection on an OLAP cube and ONLY define to have refresh on open on the OLAP connection, it loads with the error message saying that the workbook needs to be upgraded even though we haven't set the PowerPivot connection to refresh on open. The relevant data is actually updated correctly, but having an error displayed on open isn't very acceptable :) Updating to Excel 2013 is unfortunately not a possibility.

Does anyone know about this issue and is there a way around it? Is it even possible to perform a refresh on open without also doing it on the PowerPivot connection?