Yes, even if they just tightened up the spec or the inspection process, they would likely issue a new part number because it's very difficult to do recall tracking by revision number.
Not necessarily. The SW update can be to prevent the conditions that cause and out-of-spec part of fail or change the failure mode (e.g. not an instant loss of power). Or it could be to identify the parts that need to be replaced. Assuming the situation where the in-spec parts don't need all that.
I'll add a 3rd theory. The NHTSA recall cites a "part-to-part variation of the high voltage battery main contactor." They could have tightened up the spec and done 100% inspection of the parts they had and only released the ones within the new spec to the factory floor. In fact, that would...
The NHTSA chronology says "On April 12, 2022, an issue pertaining to high voltage battery main contactor overheating was brought to Ford’s Critical Concern Review Group for review."
What that means is the number of reports tripped their threshold for critical review. It's not like some guy came...
I guess I'm conflating defect rates with failure rates. We don't know what the underlying defect rate is (or if it's a design or manufacturing defect, but sounds like design).
Regardless of timeframe, 0.5% is a HUGE defect rate in modern quality control systems. Combined with the severity, this was almost certainly a brown pants moment on the inside.
Have you worked in a regulated industry? (not asking to throw shade, I'm genuinely curious; these things may seem like a mystery to those who haven't) The regulations require Ford to establish procedures to identify and classify defects, and to define a process for initiating a recall when it is...
That's simply not how the regulatory scheme works. Just because NHTSA hasn't forced a recall doesn't mean it's not required by law. In fact, if you get to the point of being forced, you've long since broken the law and are in deep sh** (see little companies called Tesla, Boeing, and Abbott).