APDS gets +2AR to reflect how armor shouldn't be as good against it.
Yeah, and that Logic is the problem here (apart from the fact that +2 AR for -1 Damage is a terrible tradeoff). The +2 AR applies regardless of
how good the armor (and/or cover) is. It doesn´t get better against stronger armor and it doesn´t offer less benefits against targets with low armor. If I understand it correctly, it even applies when there is no armor at all.
In 5th Edition, APDS (and Armor Penetration in general)
at least had a kind of diminishing return against the occasional targets with (very) low armor, because you can´t reduce armor below zero. It also offered significantly
higher benefits against hardened armor and drone/vehicle armor. In 6th Edition, it´s just a bad numbers game. APDS Ammo doesn´t really care for armor. It just
looks like it does at a very superficial glance.