You left out the rest of the title where he reveals where his information came from.
Several of the Supreme Court Judges of Pennsylvania were still alive when he published this very widely used lawbook, and they did not object. Therefore they concurred.
This work spoke for *ALL* of them and it spoke for the normal understanding of the *ENTIRE* Pennsylvania legal community.
You just don't want to acknowledge this obvious fact, because it blows a very big, and unrecoverable hole in what you wish to believe.
Your attempt to wish away this book and the sources of this information is akin to whistling past a graveyard.