I think they need to consider how all healing options tie together.
Any approach that heals less than total HP on a extended rest will have a consequence on healing for the coming day. If a fighter wakes up from an extended rest, rolls his dice, finds he is still 10% hp down from full, why wouldn't the cleric just use some resource- a healing kit or whatever- to bring him back up to full?
If healing outside of an extended rest is limited and using those resources is always an important decision, then how does the rest of the day of combat and exploration progress? Is healing so rare that the 10 minute adventuring day, or even a 20 minute adventuring week, is possible or even expected?
However if healing is available enough that giving the fighter those extra hp in the morning has little or no effect on the healing available for the rest of the day, then the game design has just added extra, fiddly steps - rolling HD, tracking kits, some extra math- to clean up and lingering damage not cured by the extended rest, or in other words, to get to the same place the simpler rule would have.
If lingering effects of injury are important, maybe the results of rolling HD after each extended rest could set your maximum hp total for the day, and no healing apart from an extended rest can raise that higher?
--Z