Not true. You can over seat a primer. Been there, done it, had the ones that didn't go bang.
It doesn't just got the bottom, the edge of the primer rolls over and locks the anvil.
I wish I had photos to show some of the things that I see at the range. One being a box of factory ammo where two rounds dint let loose. After checking the rest it was noticed a couple with primers a little deeper. Put them in and tried firing, they did not fire. Tried and tried again but wouldn't fire. Nothing at all wrong inside the case, there was powder and a primer hole. How ever, the priemers was well dented, just the same as op photo.
I bet you the op loaded the round again and tried to fire it at least one more time.