Without making a big show of this, it would have been much more difficult to get BMW's attention. Duncan tried to contact legal but was refused.
The point of GPL compliance isn't to sue or to shame, but just that: to bring people to compliance. Even in the beginning of the GPL rms said to Eben, "I have a rule. You must never let a request for damages interfere with a settlement for compliance."[2] Legal action is an absolute last resort, usually when years of friendly negotiations fail. All GPL lawsuits I know of only took place after years of attempts to get compliance failed. Duncan just wanted compliance, not legal action.
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[1] https://lobste.rs/s/uaa4db/bmw_refuses_to_abide_by_terms_of_...