Accuracy of Apple Watch

I suspect I have POTS, I didn’t think so until the following happened:

I have an Apple Watch (bought in 2022 or 2023) and my heart rate on it is rarely over 110. I had what felt like a POTS episode (I work with people with POTS frequently and have EDS). I lay down because I felt sh*t and my watch said 91bpm so I took my pulse manually and got 130bpm. So I’m starting to think that maybe I do have POTS (obviously will do a NASA lean or tilt table test) and had only excluded it based off bad data

Anyone else had a similar experience?