Confirmed in the toolset. It makes me wonder if this was intentional for balance reasons rather rather than an oversight, but I have no information either way.
I can add this of course. In order for it to have any effect though, people will either need to make new armors or "ox" the ones they have, which of course resets any customizations and resistances. Beyond this, there's nothing we can do about armors already in circulation.
Adding the property will also increase the level requirement by one level, potentially leaving some people without their armor until they gain that level.