The proxyAddress attribute should only be modified based on modification of mail attribute (general tab), if the account is mail enabled.
However, if the account is OCS enabled and you manually specify the SIP address in the proxyAddress, the mail attribute (General tab) gets published on the proxyAddress attribute.
This is occurs by design. The proxyAddresses attribute gets modified based on modification of the mail attribute from the General tab if the account has the proxyAddresses attribute populated (not empty).
ARS relies on the proxyAddresses attribute status (populate or not populated) to decide how to handle the mail attribute. By manually populating the proxyAddresses attribute (sip address), ARS believes it needs to publish the mail attribute.
Enhancement Request (TF00371889) has been submitted for consideration in a future release of ActiveRoles Server.