Pawns with the tough trait get their damage reduced before it's calculated for the shield belt, meaning their shield belt takes half damage, or in other words: Their shield belt can absorb twice the damage.
Thinking about it, this bug may also affect how much damage armor absorbs.
Just confirming that Tough does apply before armor mitigation, I remember testing and mentioning it during unstable testing and as far as I can tell nothing has changed.
It certainly makes an already extremely powerful trait more efficient than it needs to be.
Report moved to mantis.
Thanks for reporting! ;)