The author here. Although some previous work on this controversial subsystem that is comparable to Intel ME was done [1, 2], this tool aims to lower the entry barrier for looking into the code running on the PSP (and other AMD subsystems, too). The PSP is running completely proprietary, undocumented code provided by AMD. It has full access to the x86 memory and is therefore a valuable target for attacks.
[1] https://seclists.org/fulldisclosure/2018/Jan/12
[2] https://msrnd-cdn-stor.azureedge.net/bluehat/bluehatil/2019/...