GM said they don't trust the stock of packs they have in warehouses or any installed in EVs. They are requiring LG to implement GM's level of QC, which we must presume is higher than LG's existing QC.
No batteries will be fixed in any EV until GM is confident that LG can actually manufacture the cells without defect. At that point in sounds like all packs will we fully swapped in all EVs made.
My understanding is that they haven't got a way to easily detect which cells have the defects and which are fine. But that they are working on it, and may be close to a solution.
My understanding is that what they are really working on is a cost effective way to check for the defect on new batteries leaving the LG plant, so they can be confident that the replacements don't have the same problem.
* Some 2019 models were included in first recall, others in the second, based on where the batteries were manufactured.
Learning all the really hard lessons about QC and how to prevent fires and defects takes more experience and knowledge and time than any new competitor could devote to catching up.
I haven't dug into the details of the "manufacturing defect" at LG's battery plants - seems like a failure in Quality Control.
I also don't know why GM cannot just bring in the battery packs and test/replace the faulty cells, unless the problem is so widespread it affects ALL cells in all packs.