Hello. Just successfully reflashed this M/B to latest bios - see logs attached. Unfortunately, I can't bot into Linux right now from primary HDD because of its failure after reboot (I'm sure this isn't related with reflashing), but I was able to boot from LiveUSB.
So I believe that we can mark MX25L8005 as PREW (I tested all operations) and GA-MA74GM-S2H (rev. 3.0) as fully supported (see attached patches).