I recently ran into this in scanning through some forum problem reports. Typically this health rule violation is reported on a large farm installation. The health rule reports the app servers that do not have PowerPivot installed on them as being out of date. Can you read “bug?” Yes, this is one. You can either safely ignore the error report or you can disable the health rule. The problem is solved in CU3.
As always, sorry for the inconvenience. We should have done a better job in our error reporting.