@akcent svl7 told me that not all time of flash protection can be bypassed by prr/prr2. Seems that HP uses more harder protection.
The extra test just confirmed what you said. To progress in this direction test was not meaningless. I wrote to the author, but he has not responded yet.
@akcent SLIC Toolkit doesn't work reliably under UEFI systems; it can't find the RSDT pointer. Use RW-Everything.
rw files also pose a problem. I do not open. So I suggested WINPE. WINPE contains all the necessary tools.