The fighter bonus to shield AC was recently updated to also advance the parry AC shield progression, but it caps at +6 (the normal cap for shield AC granted by parry), despite the AC tooltip actually indicating that it's higher. My suggestion is to just let parry with a fighter shield AC bonus exceed the parry cap.
I doubt most deep fighter builds would take advantage of this, since the extra stats and DI from a shield offer so much (and shields like Aegis Woe already offer more shield AC than parry can already). There are a few builds who want to keep an empty off-hand that do like parry AC (chief among them being swashbuckler), but they usually don't want to dip a heavy enough fighter investment to take advantage of the shield AC. Casters also make use of parry AC, but they also don't want to dip enough fighter to get the shield AC bonus. So really it'd just give a little qol if you don't want to use an off-hand.
