V 1.3, cosmetic mods.
The HEAT perk on the grenadier does not enable incendiary grenades to shred armor. I tossed an incendiary grenade from a HEAT grenadier on a 2 armor muton centurion (rookie mode is why it only has 2 armor) and it still had 2 armor afterwards, this is easily reproducible.
The wording implies that all grenades gain one shred. Perhaps this is intended, but I can't tell really, and even if it is intended maybe the wording should say frag only grenades or grenades that already have shredding gain one more. Maybe devs could look into flashbangs as well. I'm agnostic as to whether the shred on literally all grenades would be op or not, but if it's not intended to work with emp bombs/flashes/incendiary it should just say so at least in the helper ? text.