I think we must be careful not to over observe these things. The margins are so tight that they are not only skill dependent, but include part of luck as well. The driver may judge the biting point of the clutch perfectly, but he can not gauge the grip levels and tire temperature perfectly. Also, the grip levels are not equal on both sides of the track (outside/inside), so the perfect biting point of the clutch may vary.
P1 on the potentially clean side of the track vs P2 on the potentially dirty side. Equal perfect starts by identical cars would in theory yield an advantage to the car starting on P1 (plus a sizeable chunk above).
In 2014, 2015, I felt Lewis was nigh on perfect, even when starting on P2. The Mercedes showed a clear tendency to weaker starts when sitting for too long on the grid, so usually when Lewis started on P2, he took his time while Rosberg was already lined up at the start. This meant that Rosberg had a longer 'wait' and potentially a slightly warmer clutch at that point, changing the biting point.
2016 was a bit of hit and mix for both Rosberg. Yes, Rosberg edged it there, but he had his fair share of 'bad starts' too, which led me to believe that the new starting regulations just made things impossibly hard for both Mercedes to the point it was less a skill based challenge but one with a certain element of luck.
Having said that, Lewis has dialed it down quite a bit to when you look at his 2011 season. Part of that IMO stems from the fact that he has had a very good car in recent years so playing the 'long game' has become more important than ever. In 2014 to 2016 he only faced his team-mate as a WDC challenger and at such, mistakes were very costly (potential DNF vs 25 point deficit). In 2010, 2011, 2012, the point loss was smaller because we had more different race winners and in those years he had a bigger backing by the team due to the fact that the WDC challengers were spread across different teams (Alonso / Ferrari, Vettel / RB etc).
I think this confidence and playing the "long term game" has helped Hamilton in becoming more consistent in his performance. By not being too aggressive at the start of the race, there is less risk of "throwing it all away" by a badly timed maneuver. In Bahrain, he was on the inside with less grip. He decided not to overcook the brakes (e.g. he braked earlier, fully aware he would probably need a longer braking distance being on corner inside) and that is where Vettel gained the position by braking later. At that point, keeping your nose in the corner would only result in a potential DNF for both cars, a broken front wing. By not being too aggressive, he kept himself inside the race.
There are times when to be aggressive and there are times where not to be. More often than not, I think he gets it right, even if it means he loses a place here and there. You're not always dealt the best cards. Starting on the off position sometimes means that you are at a disadvantage vs the cars on the cleaner side of the track and you do what you can.