Minidumps don't really preserve much of the PRCB, if any portion of it. It's one of the big reasons why 0x101 bugchecks are impossible to debug with a minidump, because the processor contexts are not saved, which includes the current running thread for each, the PRCBs (and therefore the PCRs), etc. The reason why the WHEA error record structure is able to hold so much information about the situation, including processor info, is because it's all generated prior to crashdump generation. It has already grabbed what it wanted from the PRCB and whatnot to generate the contents in its structure before finally the system creates the crashdump and bluescreens.
