Apple's own user guide (https://web.archive.org/web/20201223140550/https://support.a...) suggests otherwise:
>In the Messages app , you can send text messages as SMS/MMS messages through your cellular service, or ...
Also my own experience is that it at least can receive SMS text messages, just it won't show you if it's not from your carrier (if it's from your carrier, it shows you via a popup window or something, can't really remember as that was several years ago).