I don't know specifically about the PA-12 District, but gerrymandering does not in general work only to benefit one party. It works by concentrating Dem or Rep voters into districts. It helps incumbents.
To me, creating voting districts is a top political reform priority. The situation today, especially for the US House of Representatives, is that the politicians get to elect their voters and voters get screwed.
I agree. However, I believe this author was specifically referring to PA-12, so any redistricting would likely favor one party over the other here.