Note that I was also just speculating. Obviously I don't remember every detail of that session, I just quickly checked as I thought I remembered Grosjean not making it.
And I also think that it's a perception that drivers in the best cars are more consistent. It just looks that way. Because it's much easier to be more consistent in the best material. The faster the car, the more planted and easier to drive it usually is. Plus, little mistakes are harder to spot in qualifying as they simply have a larger error margin. Which also decreases the importance of a perfect lap and therefore takes off a part of the pressure.
So in my opinion I think it's really unfair to compare Kimi & Alonso in qualifying to for instance Vettel & Hamilton. Especially to argue things to be a 'fact'. While all of their cars have been quick at various stages this season, they each have different characteristics. How often has Webber not made Q3 compared to Grosjean for instance? It's simply too easy to criticize Kimi for not qualifying well enough when it's clear that the Lotus is far from pole position at most venues and that Kimi has done much better than Grosjean anyway.
Another example that just crossed my mind: Vettel confessing that his Q3 Monaco lap was messy, and the onboard showed that. Could've had pole, but still qualifies 3rd, and nobody cares. Kimi almost a second down in 5th, perhaps with a perfect lap. But who knows, because no one cares about how well someone did for P5.
I do agree with you, it does work both ways though. A mistake made by drivers down the field is less easily noticed.
I've decided to do something similar as I did above with Bahrain for the six dry qualifying sessions. Button, Hamilton, Vettel, Alonso, Sutil, Hulkenberg and Massa are the seven best drivers at extracting performance on their ultimate lap on a time basis (in order). Button and Hamilton have been pretty much faultless and easily have the best results.
Hamilton, Hulkenberg and Perez are the only three drivers who have performed their best three sectors of qualifying on their final lap four times or more.
Gutierrez and Bottas have probably been the two most inconsistent qualifiers, with both not hooking up their best lap on five of six occasions. This is particularly suprising as both have gone out in q1 on multiple times. At least two of these times has cost Bottas a place in Q2.
One of the most costly mistake of the season was in fact Raikkonen's in Bahrain, costing him three places. This may have cost him the win, ultimately this could be the difference between a championship deficit of 38 and 24 points. Vettel and Rosberg both didn't execute in Hungary and cost themself a place, meaning Vettel should have been on pole and Rosberg 3rd. This was a huge error as the Red Bull would have probably won the race without this mistake.
When taking everything into account, across the season, you have to say Hamilton has been the best qualifying performer. Difficult to pick who's been best in the races; Hamilton's had Spain, Rosberg's had Hungary, Raikkonen's had Malaysia and Vettel's had Hungary. Alonso's been pretty great everywhere although he played a part in his Malaysia accident.
I think across both categories, Vettel has been marginally the best.