(I'm not saying I want them to do that -- just curious why the lawyers aren't using that technique.)
If WhatsApp is invoking other, non-copyright theories, a DMCA takedown related to those theories would be invalid.
Still, most platforms have somekind of program like eBay's Vero service that is used to report and enforce violations of its terms of service that trademarks and copyrights not be used without permission. Which would have been the better way to go in this case.
https://github.com/venomous0x/WhatsAPI/tree/fd07b49a459cda25...
... and it didn't work, causing only "brief downtime", probably because it didn't actually fall under the DMCA.
Just another reason the DMCA is fundamentally broken.
It sounds good, we'll do this basically free for you and collect our own fees from violators. But they don't know just how much damage these groups can do to their credibility. Rolex is another company that has lost my business forever with their scam.
The law states you have to send a letter. The scam part is in demanding money or profits made from a perceived violation of IP. Companies that do that crap can die in a fire.