When did Joel Greenblatt change his strategy?

I read Mohnish Pabrai's "The Dhando Investor" last week. Pabrai wrote the book in 2006. In it, he talks up Joel Greenblatt quite a lot, second only to Buffett. And he talks about Greenblatt's highly concentrated portfolio strategy, only holding maybe 10 stocks at most.

Flash forward to today, and it's a completely different story. Gotham Asset Mgmt appears to own a tiny piece of just about everything. 1278 holdings according to whalewisdom.com's tracker.

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That's a big shift. Anyone know the story?