They had 5 days to report a potential safety problem to the NHTSA and failed to report. Here we are 7 months later, still unreported. That is why the NHTSA is investigating this. Tesla will be fined hundreds of millions of dollars at the minimum. This is a criminal matter, hiding safety risks from customers is a serious crime with very serious ramifications. A few years ago Honda was fined simply for not reporting a recall they were believed to have known about that wasn't even on one of their own parts, and one they didn't actively try to conceal. Tesla's taking action to conceal a safety problem from the NHTSA escalates this beyond fines - prison is a possibility too! This is exceptionally serious - safety is important and Tesla does not take it seriously. They still haven't addressed any safetyy concerns - and deception is never a legally allowed safety mitigation. There has been no oversight, no safety mitigation, and no repairs. It's all illegal.
If the NHTSA agrees this is safety related like Tesla claims, they will be forced to replace / repair every battery. If they are convinced it is not safety, Tesla will either be forced to uncap the software or replace the hardware under warranty. It's illegal to downgrade even slightly. Not just in safety law, but also in warranty law and property law. They can't steal and they have to repair with "equal or greater" - lesser is illegal. There is no situation imaginable where the caps remain in place and Tesla is allowed to conceal fire hazards from owners.