Not only is that true, but that firmware is a bit faster than some of the others.
However, the popular CMC discs did not have have their data integrity issues fixed until T9. Playback issues for many discs (can't find documentation) were not acceptable at maximum speed until T9.
In this example, the always pretty CMC scans got about 12% worse looking with the new firmware. Playback was improved considerably and files on the discs were valid files. Previous firmware would make a prettier scan, yet there may be corrupt unreadable data files on the disc--yes, on that same disc with the pretty scan.
I wonder if you ran into a flash problem? S9 and T9 have been a real pain to get to flash correctly on my two 1620's (retail models). One of them had to be flashed back to L9 because it was SO confused! Then I flashed it to T9. Really bad scans. So, I flashed it to T9 again. Acceptable scans, much better data integrity, and a surprise bonus:
Now discs can be burned at maximum speed, AND to my surprise, will play back smoothly in my very easily irritated set top DVD player (a dust spec sends that player into fits of hysterics).
Before T9, I was stuck at 4x to keep the irrational set top-player happy.
Despite the scan results, this (change to the new firmware) does document an impressive increase in real-life burn quality.
Yes, the scans look worse, but the movies look better.
I think that if you had more than marginal differences with T9, then flash it again. . .maybe twice. . .