The reviewers aren't all-knowing. For an app like this they could have observed the following without rejecting the app:
1. App accesses user's contacts (100% legitimate for an app of this nature)
2. App communicates to app developer's server (many, many apps do this for legitimate reasons).
It's not valid for an app to sends contact information to the app developer's server without user permission after an adequate and accurate disclosure. But of course the app could have sent that information in an encrypted form so that the app reviewers had no way to know that contacts were being sent or may have actually asked permission without revealing the intent to spam.
And, obviously, no spam was sent until after the app had been reviewed.