We did that and it is still showing the billing info before going to authorize.net. We also got an error from them on checkout:
Not able to check out: Error code 103
The authorize.net gateway we are using collects shipping/billing information on the authorize site.
That extra information may cause confusion. No need to send anything but the cart information.
Not able to find code that POSTs the API login ID or the Current Transaction Key.
I believe all information for those keys was entered correctly in the wizards.