When I did build Megasquirt EFI to one of my cars, I did learn that motor needs more fuel when starting, it is not very much of fuel, but it is more and it is quite unclean burn during startup, also it is needed to calculate that energy starter uses or if bump starting that startup energy must come from somewhere, so glide must be enough to overcome all that, pulse consumes more fuel than just accelerating from speed Y to speed X because of that.
Question is how much more it is? Making that energy back to battery with burning fuel is taking multiple times of energy because of poor efficiency of engine, belts etc.
Putting some solar cells to roof and charging battery with those, might be one solution, but they add weight and do they produce more energy to battery than what they add to consumption of fuel because of their weight?
When finding scientific reality of issue, it is needed to look every detail.
Surely P&G saves fuel, even there are these drawbacks, so that means less CO2 as CO2 is directly related to how much fuel is burned, so those interested in reducing that may continue without a worry, but those interested in air quality might need to consider upgrading engine management that can be programmed not to squirt so much extra fuel into engine during cranking and startup, even though amounts are still minimal, but if we would not be interested from minimal, then would we fill panel gaps?
That is at least how I see this subject.