If telemetry data hashes are regularly added to a blockchain, then we can be confident that the full-data set matches the hash at a later date, and are not purely dependant on the honesty of a proprietary manufacturer.
If there is a concern that the original data collected might be doctored... then this is valid, but also should be the focus of tests and legislation.
Ie,
- Currently, speedometers are legally required to be within a certain tolerance and calibrated.
- VW Diesel scandal, was discovered and hurt the manufacturer badly.
The argument that not using a blockchain for storing referential data because it might be dishonest data doesn't strengthen the argument that we should purely trust the vendor, it makes it weaker!
(That said, I think this is pre-optimising and using blockchain for this today is overkill... but long term, I could very much see this being a valid use-case)