he's in a car that is believed to be quite consistent and in a team where they seem to have the best understanding of the tyre and the effects of setup on tyres
I actually think that the Lotus team "lucked" into a car that happened to work well with the Tyres. After all, they were very impressive from even the start of winter testing, having designed their car without knowledge of the tyres and one might expect that just down to sheer randomness one team would be that much closer to having a good base setup for the tyres than the other teams.
The fact that the Lotus, while fast, cannot seem to compete to the ragged edge (bar, perhaps, Bahrain) with whatever other team has managed to win the Pirelli tyre-switch-on lottery, indicates to me that the car's luck with the tyres flatters the car, just as luck might be seen to flatter the Sauber, or the Williams for that matter. From Lotus' perspectives, they probably do "understand" the tyres, that is - they have not had to worry so much about them, but I would wager that the Lotus engineers would have no better idea of how to alter the Merc to broaden their window than the Merc engineers do.