I don't know what to say other than — you are wrong. It's extremely rare for someone without an actual heart defect to die because they exercised too hard.
Those can then cause a stroke when they obstruct blood flow to something critical. The stroke may be fatal, or maybe you just loose capabilities like motor control of half your body.
Either way, there's a reason many people are advised to consult with their physician before beginning an exercise regimen.
Stay active folks...
Also, I can't help wondering whether this study's results are applicable to what they call a "stress test" at your doctor's. Or is that beyond the regime they were examining.
The smartest way to do it is probably to increase both frequency and intensity progressively, which means your body can make small adaptations over time without putting undue stress on the joints, tendons, bones, cardio-vascular system etc.