I figured it out with the help of Jugginator. If you have the multiplayer option for player killing set to no killing then you take zero damage from these. I forgot that I set that option to no killing when I play with my girlfriend and my sons so they won't shoot each other or me by accident...
Oooohh a no killing setting bug? Where can I read up on this? I remember standing pretty close to them before and being fine. Maybe I was far enough away to not be in danger. Time to go test!
I might be crazy but I am sure that timed charges did not hurt players when placed on larger safes and locked containers in alpha 20. I could have sworn I had a play-through in early 21 where I was playing with some timed charges and still did not take damage when they went off if I was next to...