[mcnamtm1]

I think it matters how you define 'end-to-end'. Where are the endpoints? In a SaaS platform, WhatsApp could claim your device and its ingress server are the endpoints. With that definition, they can use TLS and claim E2EE.

But some people would expect the two endpoints to be their device and their human counterpart's device. Mobile app to mobile app and encrypted across all servers.