I think the reality is that soil weather and plant conditions are infinitely variable, so there is no way to do an exact representation of every specific set of conditions.
Rachio already exposes many different parameters so each can pick the ones that ultimately do the best job at tuning their specific conditions.
I do agree that ultimately it would be nice to add a layer of intelligence over the existing algorithm to make the tuning more intuitive and less technical.
Below is a recent thread on the subject