Here in California we are using bark as a topper for our flower beds to retain the water for our plants, trees and shrubs as well as for esthetics reasons. Specially now that we are in a drought. Thought maybe it could be a soil type of its own. 
It does retain quite a bit of moisture.
I have it at Quebec City, Canada
like bark as a medium? not a just a topper to lock in moisture?
Why yes, you put on a layer of about 2 to 3 inches thick and it comes in various color and sizes. 
that is not a soil type, that is just a top dressing to hold in moisture. bark as a medium i would expect to encompass the entire root ball of the plant and thus justify a soil type.
honestly outside of orchids, i know nothing that can grow in a medium with such a low cation exchange index, how would it hold nutrients? it would also suspect it to lower the available water as its drainage is fantastic
Well all I know is that in this drought we have been encouraged to use drought resistant plants with low emitting irrigation and bark. Maybe to please the masses you can have a category called mulch. Im sure everyone is familiar with that term. 
well, at risk of sounding like an asshole, i get the feeling you are asking for unobtanium as this just does not make any since to me at all…im sure the rachio guys will understand what you are asking for and add it to the product at some point.
I think he’s just asking if the Rachio should know about a mulch layer above the soil. The bark layer is not the soil, but a top dressing, as plainsane said.
The question is, does a moisture-holding layer above the soil (significantly) alter the evapotranspiration calculations for a given soil?
i would rather time be spent on a moisture sensor that the rachio could interface with. this is a fools errand as different thickness or different mulches will provide better/worse moisture retention. that is a level of granularity that has to be handled by the landscaper/owner. lets face it, mulch will degrade over time and at what rate is completely dependent on the climate where the flower bed is located.
@JNotar, you need to plug in the soil type so that the iro can make a educated estimate on how long it takes the water to penetrate to root depth. mulch will not inhibit this in any measurable way…