There are scenarios where a payer wants to use a different billing address. The integration does allow the signer to make edits that would then only be stored in Smart Tuition as a Billing Address (it does not update the ON Core user profile Home address). 

For the Smart Tuition Integration, the Billing Address is sent in one direction - from ON to Smart Tuition

In the process of setting up the integration, we needed to keep in mind incoming families (or existing families at schools who are implementing for the first time) where they might not have an existing Smart Tuition Account to pull data from.