Thanks for the clarification!
From what I see, the Iridium Go will allow you to send texts without any cell towers (on your side). You are correct in that the recipient will need cell or another active service to receive the texts on their end. However, along the same lines… If the recipient does not have active service for some reason to receive the text, they also could not receive your call to their cell phone even if you had a satellite phone. The exception would be if you were calling a landline.
If there was a situation where cell towers around the world were down, you would not be able to text anyone. You could use a satellite phone to call another satellite phone or a landline. The Iridium Go is not really designed for this type of situation. It is intended to be used when you yourself are unable to access cellular service, but your recipients are.