Keep in mind that he term "final remedy" was used specifically in conjunction with the "temporary remedy" that had come before it. This type of wording is only used to satisfy NHTSA requirements. Now that there is evidence of the "final remedy" not having the full intended effect, it is almost certain that they will be taking additional action.Found it:
Dealers will be notified on November 13, 2020. GM will notify customers pursuant to the customer notification strategy that GM reviewed with NHTSA on November 12, 2020. Owner notifications of the final remedy are estimated to occur in two phases; the first on May 13, 2021 to address 2019 model year vehicles and the second on May 31, 2021 to address remaining vehicles. The final remedy will be executed under bulletin N202311731. Until the final remedy is available, an interim remedy is executed under bulletin N202311730.
Looks like they used the term "Final remedy" when talking about rolling it out. This was a statement made before they released it.
My guess is they thought it was going to be final. That didn't work out.
If I had to guess, I'd wager that GM (or at least some engineers within GM) anticipated this was the likely outcome. After all, the educated portion of the public saw it coming from a mile away.