iMessage doesn’t use SMS when communicating with other iPhones.

apexalpha · on Oct 13, 2022

But it does fallback to SMS when communication with any other OS (I guess now just Android).

Which is kinda the point. WhatsApp doesn't do this, it works on all platforms.

a1445c8b · on Oct 14, 2022

> WhatsApp doesn't do this, it works on all platforms.

…as long as the recipient also has WhatsApp.

If WhatsApp were to support communicating with non-WhatsApp recipients, it would have to fall back to SMS, I imagine.