It still doesn't accomplish anything. There's nothing magic about the GPL as a license which can force proprietary code to be released as open-source. Emailing someone and saying "your product contains GPL'd code, so give me your proprietary source code" is meaningless.
The copyright-holder can take action against an organization producing proprietary software who is violating their copyright. Legally, they're violating the rights of the copyright-holder, not the end-user.
> The claim that a GPL violation could lead to the forcing open of proprietary code that has wrongfully included GPL'd components is simply wrong. There is no provision in the Copyright Act to require distribution of infringing work on altered terms. What copyright plaintiffs are entitled to, under the Act, are damages, injunctions to prevent infringing distribution, and--where appropriate--attorneys' fees. A defendant found to have wrongfully included GPL'd code in its own proprietary work can be mulcted in damages for the distribution that has already occurred, and prevented from distributing its product further. That's a sufficient disincentive to make wrongful use of GPL'd program code. And it is all that the Copyright Act permits.
https://lwn.net/Articles/61292/