Well, seems to be some corruption here.
But:
1.) How did you manage to read a 4 MByte SPI and get an 8 MByte file?
2.) How often did you read the chips? Did you get 2 identical reads to confirm good dumps?
To keep it simple:
Save the padding from your bios- region (in the complete firmware image from 0x640000 to 0x690000)
It starts with “DVAR”
(There’s 2 DVAR blocks starting at 0x640000 and 0x648000, just copy the complete padding)
Extract the bios region from update A14, exchange the corresponding area with the saved padding.
In the stock bios that’ll replace the two opened dummy efi volumes.
Exchange the corrupted bios region with the stock bios region from update which you prepared with your padding.
If in doubt clean/reinitialize the ME according to
Flash both chips back, read the content after flashing in a separate process, save dumped new content with different name and compare to original, no difference is allowed.