most perks like that only check for chest armor. not a bug.
Weird as ingame it's mentioned as "While wearing no
heavy armor, gain +25 Evasion, +10 Attack Power, and +10 Critical Chance.", by that i have alway's assumed it was any heavy armor, and no particular specific piece.
Edit: Verified it and it's true, yet if so intended probably the description should be changed to Heavy chest Armors only for better understanding (also for all other similiar perks).
Yet that also makes itemization choise in various classes builds that use this kind of
Perk mechanics much more harder to do.