Both your linked fact from the University of Arkansas
When you sneeze, the intrathoracic pressure in your body momentarily increases. This will decrease the blood flow back to the heart. The heart compensates for this by changing its regular heart beat momentarily to adjust. However, the electrical activity of the heart does not stop during the sneeze.
...as well as your 'myth' from webMD
For instance, it's not true that your heart stops when you sneeze. When your chest contracts because of a sneeze, your blood flow is momentarily constricted as well. As a result, the rhythm of your heart may change, but it definitely doesn't stop.
...come to the same conclusion, namely the heart does not stop during a sneeze.