Do Application defaults work on a MAC using PS3 GPD?
What defaults? Macs typical used the last used settings as the default. I have no idea what PS3 is referring to and the GPD is a Windows only driver, you need to clarify the question.
There is no Mac equivalent to the Xerox Windows drivers (Global,Native and PS and PCL variants) Saved Settings feature, closest option is to use Mac Presets.
I tried with Last used settings in Apple's Presets menu, but it carries the settings from the last time the printer was used no matter the source (not what you are asking for). So it would seem the answer is no, you can't replicated the Windows drivers feature Saved Settings within any of the Mac drivers, I don't know if the reason is that it cannot be done, or if it simply wasn't developed by Xerox at all.
If you need a full statement, you will need to call in and speak to 2nd level support and they can forward the question to the Engineering department