Wait, if this is a known safety issue with batteries, why isn't there an engineered capacity head room? Set the max charge to the cells' 90% capacity, but report 100%.
That's what they already do. With lithium batteries neither 100% nor 0% are at the physical limits of the cell, they are both software limits. They might be enforced at the battery pack (over/undervoltage protection) or higher up in the chain.
It sounds like GM set the level too high, but it could also be something else like a problem in the battery's thermal management that is fixed by limiting the maximum charge level.
