No , that did not look like a glass jaw to me. Jacobs was hurt maybe once or twice throughout the fight and suffered a knockdown but that was more so balance. He was very motivated and hungry against Golovkin so his heart played a role in it as well. Overall his chin held up pretty well.
The other thing about the Pirog fight is that Jacobs looked like he was going to bounce up. He was definitely hurt but the ref was WAY premature in the stoppage. It appeared Jacobs was clear headed when it was stopped. He made the mistake of just lying there for a while after he was knocked down. He should have at least gotten to a knee.
Agree, dude was wobbled a couple of times (at least once by a jab) but took some solid shots only to fire back hard immediately. No glass there.