I was asked about my research, but I'm not sure I would call the questioning "in depth." Many people were in the same field, some with basic science labs, but none had gone so far as to read my papers or ask about the scientific nuances I struggled with at the end of my PhD.
In my epxerience, the PSTP structure was much different than MSTP, with much less at stake. PSTP is not as rigidly structured nor financially involved as MSTP. In addition, as your time is dominated by most residency programs according to ACGME guidelines, there's a lot less room for input/schedule manipulation/research time. PSTP admin can weigh in on who they want in their residency programs and fellowships and certainly help pave your way into junior faculty, but I think it plays a much smaller role in residency than in med school/grad school training, with the exception of certain specific hospital programs.