Authorize.net "require email setting" fails for Event Register page but works for Contrib Pages

This is an odd one, but it may be indicative that something in the Event Registration code (as it communicates with Authorize.net) is not passing the email to authorize.

To replicate turn on the "email required" in authorize as described here: http://forum.civicrm.org/index.php/topic,27255.msg127353.html

Use a profile that contains email. Use this profile on a Civi contribution page, and there is no error. Do a Civi event registration and the processor error: 33: email required is given

I have replicated this bug locally. Cannot on demo site without authorize test account