I think the point
@Ray B is making is that the paddles can NEVER call upon friction braking while the pedal MAY use friction braking. However IMHO, in normal use, ie moderate braking, there is no difference in regen.
It is hard to be dogmatic about very much in Honda Clarity engineering, because so very little is released to the public. I have kept at it by looking over their work published on previous generation of their cars, or similar cars, but one can never be sure what the heck they are doing. So all that I write on this and other topics can be easily set aside by reverse engineering or a glimpse of true information from Honda.
Having said all that, I speculate that there are three strategies for 'cooperative braking' using the brake pedal - that is, regen braking + friction braking - and they come down to what this reference (
https://www.mdpi.com/1996-1073/10/11/1875) describes as 1) Serial Braking, 2) ECO braking, and 3) Fuzzy logic :
1)
Serial Braking - Rear brakes are always engaged, the front divides the work between the regen and the friction brakes
2)
ECO - Regen is engaged to their maximum capability and any extra braking effort required is then split between the front and rear friction brakes.
3)
Fuzzy logic - a complex blend of regen and friction using numerous inputs to maximize regen, safety, stability, and feel. In the reference that these figures came from, they call it 'Racing mode control strategy'
Based on how complex Honda has made the Clarity, I would expect that the 'Fuzzy logic' approach is what they employ, and it would be impossible for general users to decipher exactly what is going on without investing serious time and resources. The end result is likely to be something as is described in this braking scenario (mild, followed by moderate, followed by heavy braking):
In the paper, they explain how the ECO strategy is far superior in terms of efficiency, but you have to realize that all of the braking bias is in the front, and then it switches to a front/rear split which is quite destabilizing. Especially if you are at a slushy off-ramp and suddenly have to avoid something and brake. With a dramatic shift in brake bias, these kind of situations can be very difficult to manage for the driver and the driver assist systems. That is why I believe that Honda would prefer having a somewhat uniform brake bias and then maximize the efficiency only after safety and stability are looked after. It may not be the correct answer, but I would think most car makers are skittish about new technologies like cooperative braking by wire, and will err on the side of caution rather than simply maximizing efficiency.
Just guessing...
PS - keep in mind that this car, although front wheel drive, is a little less front biased in weight distribution than typical sedans due to the heavy battery under the floor and below the rear seat. So I think rear brakes may play a little more role than would be normally expected compared to a garden variety sedan.
