As far as I know MacOS can not do DSD 1024 natively. On my Windows PC Audirvana can do DSD 1024 through the ASIO driver, but also not through Windows natively (via DoP or WASAPI). This is not an Audirvana limitation, but hardware/OS limitations.
PCM 1536 is so absurdly high that I do not know of any gear (be it streamers or computers or source material) that can do this at all. This seems more like a sort theoretical maximum on the Denafrips than a realistic/practical one. Not many (if any) programs or devices can handle such rates.
The most logical way is to ask Denafrips for an explanation how (and with what music software) you can play PCM1536 and DSD1024 on a Mac computer on the Pontius II. They are after all claiming that it is possible.
As i already said: I am not aware of any source material in PCM1536 or upsampling algorithms that can do such absurdly high PCM rates. It almost makes me believe there must be some mistake in Denafrips’s specifications. But the only way to find out is to send a mail to Denafrips.