Winning formula

For the first time in what feels like years, I watched a Formula 1 qualifying session today.

For those that don't know, the format has been changed.

Instead of having an hour to produce the fastest lap, drivers now have two fifteen minute knockout phases with no set fuel load, where the six slowest cars are eliminated at the end of each phase.
The remaining ten cars then have a further twenty minutes to produce the fastest lap time with their fuel loads set to the same level as they intend to start the race with tomorrow.

Whilst I would have to agree that the two fifteen minute knockouts have made the qualifying session far more exciting, I find the final twenty minutes a little pointless as it seems to be more of a case of who can burn the most fuel in about fifteen minutes.
The drivers know that a car laden with fuel cannot lap as fast as one that is nearly empty, therefore they'll burn as much of their race level fuel as possible before completing a flying lap. Although formula 1 has never really been the ecologists friend, even this seems a tad wasteful by its standards.

I understand that the policy encourages teams to be more tactical (Renault are believed to have qualified slower because they intend to have more fuel at the start of the race) but it seems an awful shame to waste a ton of fuel just to encourage more gamesmanship.

Why not have the same rule for the last phase (starting grid fuel levels) but limit the number of laps that the drivers can complete?

If they only had (for example) four laps this would still give them two attempts to set a fast time (which is the number of 'flying laps' that most of the final ten cars put in) whilst having to offset this against the fuel level tactics for the race.

I'm sure it won't have Greenpeace nominating Bernie Eccleston for a humanitarian award but something is surely better than nothing?