I found something interesting. Not sure if it is a bug or by design, but when you are on a phone call with an Apple Watch Series 5 GPS model, you can take off the watch, then put it back on your wrist and it will not auto lock while you are on the call. It seems kind of wonky... If someone grabs the watch from your wrist while you are on a phone call, they can put it on their wrist and have it unlocked?