Both matches are finely balanced going into the last series of classical games.
The Petroff doesn't have a reputation as a spectator's favourite, and indeed after a solid display from both players another non-event draw was agreed. White had the nominal advantage of bishop versus knight, but Grischuk obviously decided that it wasn't enough.
My feeling is that a match of 'only' four games induces excessive caution from certain players who realize that a loss is tantamount to elimination.