According to the 6.3.2 Upgrade Documentation (in the Documentation section of this website), you do not need to upgrade the App & Reports servers to 6.3.1 before upgrading to 6.3.2. You can go directly to 6.3.2.
However, note that there are steps you need to follow in order to do this correctly. Make sure you follow the individual steps outlined in this PDF when you perform the upgrade. It is a simple process, but if done incorrectly, you can cause problems in your database.