If you saw the "BIOS update [was] successful" message, it should theoretically mean it did update; however, because of what you describe, I'd recommend the following:
1. Reboot into BIOS. Once in the BIOS setup utility, press <F9> to restore BIOS default settings.
2. Reset any customized BIOS settings.
3. Clear all DMI event logs by setting the option to "Enable", which is located in the Configuration/Event Log section of the BIOS Setup utility.
4. Press <F10> to save the new settings and reboot the system, and see how the Operating System detects the BIOS version.
I had the same problem with my new DZ68BC board. Executed the BIOS update from Windows 8 (developer preview). Didn't work. Revision stayed at v21.
Downloaded the .BIO alternative and upgraded the BIOS by using the build-in flash option (F7 key). I just had to browse to the just downloaded .BIO file (it is actually real cool that the BIOS can read this .BIO file from the NTFS partition, no need to create a bootable usb or a floppy).