SMS and
MMS text messages use the telephone network and telephone numbers as sending and receiving addresses so it is logical that blocking a telephone number would effect both phone calls and
SMS/MMS text messages.
iMessages are an
Apple only convention that sends text messages to other Apple devices via the email system using email addresses to identify the sender and receiver. The confusing factor here is Apple uses
the same app for SMS, MMS, and iMessages the only obvious differentiation is whether the address is a telephone number or email address.
