I've only seen anecdotes, not clear numbers

Not sure how you came to that conclusion. The "claim", a black and white, "Tesla redacts everything, everyone else redacts nothing" was never really a claim. But what IS not false:

There is a bunch of data that is "missing", both from Tesla and other manufacturers.

Tesla declines/redacts data far more than other manufacturers, to the point where in many cases, the majority of data is redacted for a given incident.