That used to be the case but not anymore.
Take a closer look at your link to the 17th. It says that it contains all parts of Allegheny County that are not in the 18th.
The 17th was gerrymandered to give the Dems an edge in that district.
But the Boilermakers UNION endorsed Trump.
I drive past their union headquarters on Banksville Road and see great big Trump Pence 2020 signs.
Boilermakers have awakened. I hope other union guys in Pittsburgh have awakened as well.