It doesn't work for me. I just recently noticed it, on my second heavy armor character. My current armor rating on my 30-ish warrior is 457, but I didn't get no extra armor by purchasing this perk. I have Ebony set with Ebony mail armor (I thought that might be the problem, but it isn't). I tried with Blades's armor, I have full matching set, but still no additional armor by perk. Basicly, it doesn't work for -any- set, matching or not. Tried combination with shields aswell. Nothing.
I assume this is perhaps well known by many, but not by me. I googled this issue but nobody has any constructive feedback at all. Anyone has any ideas/tips/explanation?