From the guide…
" Engine Firmware Regions (RGN/EXTR):
The Type of each Engine/(CS)ME firmware Region can be either Stock (RGN) or Extracted (EXTR) . Stock are clean/stock/unconfigured images provided by Intel to OEMs. Extracted are dirty/extracted/configured images from various SPI/BIOS. The Engine firmware at the system’s SPI/BIOS chip is always EXTR , generated by the OEM after configuring the equivalent RGN with the appropriate system settings."
Not advisable but you can try it and re-initialize the engine with your OEM settings, ensure that you know how to recover the system by any unexpected results.
Still…the repository has the pretended FW…