I think the math is very simple on this. If less than 5% of Bolt EVs have faulty separators, replacing a few thousand modules/packs is several digits cheaper than replacing every Bolt EV pack. It's also less wasteful.In Korea (where LG and Hyundai both have strong backers in gov't), LG will pay ">50%" of the cost to replace batteries in 25k Konas in Korea (on another site, I read "2/3 of cost", and LG is probably going to split that with the manufacturer of the separator film).
In the US, GM should have a far stronger position in court vs LG Chemical of America. With precedent set in Korea, it should be a "slam dunk" for GM to hit LG with 2/3 of the cost of battery replacements. If I were GM, I would run, not walk, to court and file papers against LG.
Could GM really be pushing a software solution to avoid paying a small portion of the cost of battery replacements? At this point, anything GM does which may keep affected batteries on the road (including a GM software change) only transfers liability from LG to GM.
The question of whether the software change is good enough is moot. LG can be made to pay for new batteries. The more GM talks-up a firmware solution being good enough, the more it undercuts its future court case against LG.
To me, the only justification GM would have for replacing all of the packs is if either all the packs are faulty or they feel the value of positive PR and advertising outweigh costs of replacing packs unnecessarily. However, $500 million buys a lot of positive press.