The beer ACTUALLY is warmer in the middle of the vessel. The key here is not the temp but how steady you can make it. If you want 64 and the therm says 64 that is fine but during every active fermentation it's warmer in the middle. BUY - keeping the temp as steady as possible is the key.
WITH THAT SAID - temp control is just one more thing that while it only plays a small role and is not critical in making good beer. It IS critical for making GREAT beer. But in making GREAT beer there are probably 50 more tiny seemingly insignificant tweaks to make.
Grinders Island Brewery - Pipeline
Bottled! Award winning East India Porter, Oatmeal Stout, Milk Stout, Saison fermenting at a nice controlled 85 degrees (up from 70) as it should be - weird isn't it.