Heavy Mail & Noisy Scale

Reading through the equipment section, Heavy Armor is usually has either the Heavy or the Noisy Quality. Heavy Armor comes in three main forms: Mail, Scale, or Coats of Plates (CoP). Under the descriptions, Mail is generally Noisy while the other two types are Heavy. OK, so far, so good.

There are two entries that deviate from this pattern, and that’s why I’m here. Heavy Sleeve or Legging only lists Noisy. This makes sense if the piece is Mail, but if it is Scale or CoP, would it not be Heavy instead? Likewise, the Helmet or Coif only lists Heavy. This makes sense for Helmet worn with Scale or CoP, but should a Mail Coif be Noisy instead?

In all cases, I am aware that it takes 3+ Heavy or 2+ Noisy locations to have any effect, it just seems odd to me that the rules for Chain=Noisy & Scale/CoP=Heavy is altered. Is it specifically because of the way piecemeal armor interacts (to keep someone from covering 2 locations with Heavy and 1 with Noisy and taking neither penalty)?