Oddly enough the dev replied about a year later to the same thread. the single player part no longer requires net access, only thing that does is the MP part of the game.
steamcommunity.com/app/879000/discussions/0/4492858093763771135/ Link
gyazo.com/a7745b03c6d94776525ed4fd9c00734c Link
Yeah, would be kinda sweet to have a trainer as the Campaign is quite unforgiving, in a good way.