I just put a weak magnet on the lower left side of my Barryvox S while it was in "transmit" mode. It turned off entirely for a few seconds and then rebooted with an error code until I moved the magnet away. This was repeatable with the weak magnet (a small magnetic pickup tool), so I got my Artic Cat leash, which has an even weaker magnet. I couldn't turn the beacon off with the leash. From what I've seen, the DuraPro leash uses a much stronger magnet than the Artic Cat.
I tried the same thing with a Tracker 4 and couldn't make the blinking light turn off with the magnet, so I didn't try the leash.
These are the only two beacons I have in my house. I didn't use a searching beacon to test the transmit of another, because there's just too much electronic noise around here for that to be reliable (the searching beacon would be erratic regardless of a magnet near the transmitting beacon).
I believe the first I heard of this problem was with an earlier model Pieps DSP. I also think the clamshell style Ortovox uses a magnetic switch. There may be others.
The key take-away for me is to do as FatDogX did - test your gear and determine for yourself if you're comfortable with it. There are too many beacons made by different manufacturers, and then different generations, for a blanket statement one way or another.
Your very last line is spot on my friend!! Take the time to know gear and be comfortable with it!!