Not if Hamilton came in one lap before Rosberg, there would be no conflict and no "stacking" in the pits.
That is my point.
Why does he have to wait for Rosberg.
Or even vis versa if Rosberg was behind.
Come in as soon as the times drop off and the driver "feels" the grip going.
Its a team sport, with these tyres the undercut works. No point letting them choose and stopping early. Its what it is.