I'm sure you've seen some passionate preaching in your lifetime, but I guess the nerds at Apple aren't aware of just how violently some pastors gesture in their sermons.
The watch thought he fell, but he was just gesturing REALLY hard.
(They program these watches to know the difference between regular motion and falling hard on concrete, if that gives you a clue of just how powerful Piper's gesticulation is!)
You know what, my phone is telling me that I fell down.
I'm okay. I did not fall down. Did you hear it? This has happened twice in my life, I'm preaching and they think I've fallen down. I've not fallen down.
I'm standing up! I'm preaching! Good grief, Apple!