Why is the ECG app age restricted?

I have an Apple Watch series 4, and was trying to set up the ECG app. After putting in my birthday (I am 21), the message “The ECG app is not intended for use by people under 22 years old” popped up, and I was unable to continue.

Obviously I could just put in a fake birthday if I really wanted to, but most of the few websites I could find that even mentioned the age restriction also said that doing this is risky and might be a bad idea, but not why. So, does anyone know the scientific/medical reasons that the ECG app is age restricted?