Just like OBD, I think api access to data like this should be open to the car user. If the manufacturer is taking the data ( as they do with my renault zoe) then it should be available to the end user at a standard API which is available across all manufacturers, so if you change car you can just point your setup at a new endpoint with new credentials and all the endpoints and responses are standard, just like OBD2 is
(yes I know manufacturer tools go deeper but that's another issue)
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