I got the M/L for the 41 mm even though the S/M fitted me. The small felt very insecure due the few magnets overlap. Only 5 to 6. As opposed to the Medium with 10 to 11 magnets overlap. I have tried pulling the watch as Shown in the video but in my case it doesn’t come off easily. Like… at all. A casual thief would have to give it a very strong yank and I’m not sure that would work.
I have also caught the end of the strap in clothes and it closes right back on. Again, thanks to greater overlap area. Had I stayed with the Small size maybe I’d have a crashed AW by now
Well, considering the cost of these devices, we are naturally concerned with someone yanking them off our wrists, but I dare say it couldn't go unnoticed even if someone were to pull off a successful yank, so we may be able to take preventive steps. On another note, the force required to pull off this yank means we might as well have allowed it.
This can't be pulled off casually as that (in)famous video shows the child being able to pull the watch off. It is a case of faulty magnets and/ or too less magnetic overlap in my opinion.
As you are noticing, the larger sized band works great for you (and for me, too) in large part due to the greater magnetic overlap, making a slip of magnets difficult.