That's somewhat simplified, but yes, you can temper chocolate just by controlling the temperature. I find that I generally need to drop the temperature in my Savage Bros tempering machine lower than 86F, though, to jumpstart the crystallization process before then warming the chocolate to its final working temperature.
A 'normal' dark chocolate tempering process would be something like 120F > 82F > 90F. It may be that the chocolate company you visited didn't have to go so low becasuse they were cooling more slowly, but it's the same general theory.
The reason this works is because cocoa butter crystallizes in different forms at different temperatures. By cooling to the low 80s, the cocoa butter starts crystallizing in forms 4 and 5. When you then warm it back up to 90 (or so), the type 4s melt away or change into type 5s, leaving you with only type 5s, which is what you want.
Note that even that description is pretty simplified, though. :)