Catalina had been available to the public for testing since like WWDC; unless these were late breaks only found in GM, it's a tough pill to swallow that these urgent bugs couldn't have been addressed before GM shipped.
Leaving such a small window between Apple getting its act together with the GM, and a hard deadline for third parties to get their act together, is rough.
That's exactly what the article and the quote above says there was:
> we immediately finished fixing any new crash or issue we could find over the weekend
NEW crashes or issues. In the GM. In four days.