These agencies care about safety. The fact that whatever Tesla did seems to have stopped the fires means they won't be opening investigations. They have limited time for investigations so they certainly won't be spending it on something that doesn't even seem to be a current problem. And they certainly won't be spending time investigating a few cars experiencing some advanced battery degradation.
Edit: and no, NHTSA isn't 'due' to investigate the issue. If they were going to they probably would have started a long time ago. The evaluation of the default petition sent by the plaintiff's lawyer was done because it's required by law.
What worries me (from the point of view that Tesla cars are alleged to have significant fire related safety risk) is that for a while (and may be at any time time ) has there been evidence that Teslas have more fires than other cars? If I'm wrong on this, I would appreciate evidence to correct my understanding. Not links to a bunch of media stories about Tesla fires. I've followed those. Out of a population of n cars suspected to be effected (capped / restricted) how many fires, when and evidence supporting exact cause. How many total fires have there been in the same population of the type that have since been capped?
A safety investigation will focus on data relating to..... safety, not consumer law or legal breach.
Ever since lithium and newer lithium based batteries have found there way into mainstream consumer products, they have been recognised as posing a risk of fire if damaged or abused. Same could be said for gasoline, aerosols, propane, hydrogen.... The high energy density that is so desirable, comes at a cost and an obligation on designers as well as users. If the established and accepted norms for cars are based primarily on gasoline fuel, then what's currently regarded as safe will unavoidably be based on those norms.
My first battery bank for my PV home storage uses 8 huge, heavy lead acid batteries that are only discharged to 50% for longevity - just to avoid using lithium in my house. Three years later, I added the same useable capacity with LG Chem lithium (manganese I think) in far smaller volume. 4 years later, still no fires, but if space wasn't an issue, I would prefer to be all lead acid. High energy density has its price.
So, if by tweaking the charging specs Tesla can get away with the argument that there isn't and wasn't ever a safety issue, then the discussion ceases to be about safety.
For me, unregulated OTA updates is the big issue. Coincidentally, capping etc would not have been forced on owners had there been a reasonable procedure controlling OTA. And yes, this may have revealed an underlying safety issue that Tesla may have used OTA updates to mask). Every change made to cars by Tesla by whatever means must be of clear purpose, fully documented as to what will change, and allow benefits to be had without forcing downgrades.
I don't want farts in exchange for a broken USB media player. I should not be forced into a range downgrade in order to have other features like camera viewer. If you sell me a feature (like FSD) sell me what I will actually get today, not a promise of what I might get tomorrow along with whatever unsolicited downgrades and bugs Tesla decide to send my way. Every interaction Tesla has with my car must be open and clear of purpose as well as of reasonable quality and no enforced detriment. In some ways the very existence of the OTA update facility to 'fix bugs' (as well as adding features and new bugs) does also acknowledge the existence of bugs that need fixing.
There might yet be a proved safety issue (I'm not sure if what Tesla have said in the past fully accepts 'we have a design flaw that means our cars represent an unacceptable fire hazard' ) , but Tesla MAY have dodged fire safety concerns by avoiding further fires. The other angles focused on OTA access to cars seem just as important and cover a broader range of concerns including knobbled performance.
