Let me rephrase that: AT Guns can kill pretty much any non-doctrinal Allied tank fairly quickly without armor piercing shells, in comparison to the speed at which Allied AT Guns kill Axis tanks without armor piercing shells.
And if they buff the whole Tiger, Pershing needs King Tiger Armor and 33% penetration increase.
Then your quote is misleading, you should state "the speed at which Allied AT Guns kill a Panther without AP shells", since a Panther is a whole hell of a lot different and more expensive than a P4/STuG/Ostwind/etc