To say that the choice to use eMMC is the fault is to say that ANY use of flash storage is a faulty decision.
If there is sufficient space on the drive to mitigate write amplification, then the media will last a very long time indeed. Longer than the drivetrain, certainly.
The problem is that Tesla doesn't delete logs it has collected from the cars. All Tesla vehicles (as I understand it) upload their logs more or less continually. Currently, the firmware on the cars doesn't delete those logs once they've been uploaded, presumably so that they're available when it is time to service the vehicle.
The disk filling up due to bad log file hygiene, coupled with the fact that the storage is flash-based, together cause the issue.
A simple firmware update to the eMMC chip could make it use a wear levelling algorithm that really does spread writes evenly over the whole chip.
Current implementations simply use a sector till it goes bad and then using a spare till that goes bad, etc. After 1% or so go bad, the whole device rejects writes entirely.
With a decent implementation (like ssd's mostly do), you will never be able to kill a card in a lifetime.