It seems odd that the controller is recognized by windows, yet no drive letter. I would be very surprised to hear that it's an actual BIOS issue. Typically operating systems only need the BIOS/UEFI to get up and running and then take over completely. (with a few services provided like time)
Like this snippit from wikipedia:
So if Windows can see the controller and it's not disabled, than *I* think any floppy driver letter issue would belong to Microsoft.Services
EFI defines two types of services: boot services and runtime services. Boot services are only available while the firmware owns the platform (before the "ExitBootServices" call). Boot services include text and graphical consoles on various devices, and bus, block and file services. Runtime services are still accessible while the operating system is running; they include services such as date, time and NVRAM access.
I unfortunately cannot confirm as I use Linux, don't use UEFI, and I don't have a floppy drive in my computer.
A "known issue" by ASRock doesnt make it ASRocks fault lol.. It may very well be, but I think you may have made some assumptions.
Admittedly ASRock support is SLOW.. but they are a good bunch of people that are helpful, once you get someone.
Give Emily a PM and see if there is anything ASRock can do or are doing, or ask them if it's a BIOS or OS issue.
I know you are frustrated and need to vent. But getting to the bottom of the issue and getting it resolved is what you are inevitably after, right?