This wasn't a trivial technicality. They said users' phone numbers were being anonymized and they weren't. How they handle private data, especially if they lie

This wasn't a trivial technicality. They said users' phone numbers were being anonymized and they weren't. How they handle private data, especially if they lie about what they're doing, does really matter. End-to-end encryption doesn't mean anything if they secretly keep the a key able to decrypt it, which is basically what they were getting fined for.