The author concludes that the report won’t be effective. This is based on the following:

In order for the report to be effective, the commission must speak with a unified voice.

Individual members of the commission have repeatedly expressed their own opinions about stuff related to the report before the report was completed.

We have a premise that tells us what’s required for the report to be effective — the commission must speak with a unified voice. So if we can learn that the commission is NOT speaking with a unified voice, then the report won’t be effective.

Do we have enough to establish that the commission is not speaking with a unified voice? Not quite — the other premise tells us that individual members have expressed their own opinions before the report was completed. Does that constitute lack of a unified voice? We don’t know. To make the argument valid, then, we want to establish that if individual members of the commission speak about stuff related to the report before it’s completed, that implies the commission is not speaking with a unified voice.