I can't see why the fuel effect would be less for Monaco, it's all acceleration and braking, both are adversely affected by weight.
If Jenson had speed to spare, and only risked missing the cut through traffic, it would have made sense to fuel him for multiple laps. But that wasn't the case, he needed the advantage of low fuel to have a reasonable chance.
I'm pretty sure that Jenson did a 6-lap run at the end, the official lap times don't seem to record his in-lap, presumably because it was started after the chequered flag.
14 P 3:36.075 - in pits, effectively part of inlap of previous run
15 1:25.201 - leaves pits, outlap (every driver recorded these times after a P)
16 1:15.536 - 1st hotlap
17 1:33.593 - cool down lap
18 1:15.826 - 2nd hotlap
19 - not recorded inlap, lap 5
So 5 laps. So you suggest McLaren should have let him done a 3 lap run, saving him 5kg's of fuel winning him a theoretical tenth and a half (still would've failed) with the risk that, while driving at Monaco, any tiny thing, from a yellow flag in a sector to a car slowing down in front of him, that could disrupt the lap would mean he's automatically out as he'd have no second chance. I'd be furious if that happened, and so would you. It's like what happened to Hamilton a year ago, sending a car on track with a risky strategy and just waiting for the inevitable. Why would you want McLaren to fall in those traps again?
Blame McLaren all you want, I'll keep the blame on Jenson for having the same pace during Thursday Practice 2 as during frickin Qualifying. Nothing McLaren can do about that.