Chance of Spell Suppression modifier doesn't have the DEFENCE tag.

This is a defence [sic] modifier. It should have the defense tag (defence). I just realized (this obviously) defensive modifier doesn't have this tag so I've been wasting trying to roll Suppression with harvest-defence rerolls.

its not a bug, its a design choice to make it harder to get.

You might also notice that Chance to Block doesn't have a defense tag. Resistances don't either.

Defence refers to the base stats provided by various armours: Armour, Evasion Rating, Energy Shield, and Ward. None of these are Spell Suppression, so Spell Supression does not have the Defence tag.