Just wanted to share a successful downgrading experience with this method, but also a couple tips that might help folks if they run into similar problems. I have a new LG WH16NS40 and I used the Windows 7 method. My motherboard has two SATA controllers and my drive is plugged into the Intel controller along with all of my hard drives. The DOSFLASH tool did not recognize any drives. I swapped the drive onto the ASrock SATA port, which has two ports on my motherboard that were unused, and it saw it right away. However, while reading the original firmware, the entire Windows 7 instance froze up completely multiple times, once at sector 30, and a couple times at sector 2. I just kept re-running it (after having to do a hard power off each time), and the last time I kept moving my mouse while it was reading...have no idea if that actually helped but in the end it worked! The other thing I did was I was originally saving the firmware to the USB drive, but the last time I saved to the created "my documents" folder. So that might have been an issue as well. I used the automatic data mover program to merge the ASUS 3.02 firmware, and then wrote the new firmware to the drive (all in the same Windows 7 session)...and held my breath because if it froze again I didn't know if the drive would be recoverable! It worked find though and after a reboot my drive identified as an Asus!
I've been trying to rip Spider-Man: Homecoming for a few hours (after a failed volume key for Deadpool 2), expecting it to go pretty quickly because previous regular blu-ray rips went fast with this drive, and I read that the Asus firmware is faster, which is why I did the crossflash. It's only been reading at 2x though, and failed the first time with several errors, presumably due to some smudges on the brand new disk. I'll try re-ripping some regular blu-rays though to see what the speed looks like, as perhaps it's just the UHD format. (And while I'm typing this, the read speed just jumped to 27 M/s, 6.5x, after 30 minutes of ripping.)
Anyway, just wanted to say thanks to everyone for all of the information on here and providing some useful tools to allow us to enjoy our movies!