At least in the Xbox version of DKS that only tells you the amount of time you spent in conversations, not the total time played.
I'm pretty sure now that the time showed is indeed the gameplay time. There's been times when I haven't spoken to anyone and then when I go and speak to someone, the counter has a few hours gap so it must be based on gameplay.
In any case I've noted that my playthrough on nightmare difficulty is taking longer. The counter says 27 hours and I'm pretty sure it'll be around 33 hours when I finish Ego.