To add to this, looking at figure 4, why is their "average" heartbeat so messed up? That's not what a normal average heartbeat looks like. P is too flat, Q is too big, R is blunted, and there's an extra wave between S and T that's not supposed to be there at all. If their "healthy patient" ECGs were bad enough to produce this mess on average, it's no surprise their AI had no trouble telling the data sets apart.
(For comparison, the "CHF beat" looks a lot more like a healthy heartbeat.)
(For comparison, the "CHF beat" looks a lot more like a healthy heartbeat.)