'Jacobo the Slow' is a moniker I've heard thrown around the Amazon Room recently, whether it's a new creation or not, I am unsure. It's certainly not a slight on his play, and won't be referring to any mental deficiencies, but simply an observation of his meticulous, calculated and well-thought out style of play that has served him so well thus far.
He takes his time on almost every decision, ensuring that every play he makes is the right one. From what I've seen, he has made very few mistakes indeed, so it's clearly an effective approach.