A statement that is not hard to understand.
All the SEO studies completed to date, point to the fact that if you use all the big five social media platforms, Google+ carries more juice for social signals, which effect your Google ranking as far as organic search is concerned.
We know it's all a numbers game. The numbers come from 'signals' from over 200 different areas (according to the Google Blog). Social Media only encompasses a certain number of those signals.
Social media is not everything, but it is something (of which no one is absolutely certain). So be there, be active and learn this platform if you have not done so already.
All social media is good for business, positive vs. negative considerations aside, of course. Being active on Google+ really is a smart move.
"It's no secret. When engineers built Google+, they constructed an SEO juggernaut to dominate search results above all other social platforms. Although Facebook and Twitter are essential to marketing efforts, both restrict Google from accessing much of their data. This limits their SEO effectiveness." --- Cyris Shepard at The MOS Blog