How are you measuring the full load to know it's at 12%MC? Are you splitting each piece and checking it with a meter before loading the stove? Are you correcting for temperature and wood species? That's about the EMC for your area, how many years did it take for the wood to reach that point?
For me I've never noticed a bit of difference from stuff in the mid 20's to my best stuff which was css in 2009. Mid 20's on a meter is 20% wet basis which is fine for an EPA stove.
The lions share of my wood winter 2014/15 was felled by me in Sep/Oct 2013, split over the winter and seasoned on pallets on cinder blocks over the entire summer of 2014. It was split and stacked before "break up" and moved off the racks onto the shed after freeze up. Freeze up is when you can go barhopping on a snowmachine on the river without driving a car on the street. Break up is when the spring melt is far enough along for the ice to break up and flow downstream.
I bought a new weedwacker this year and trimmed the grass around the woodpile more often than I mowed the lawn. My sunny side medium birch splits and shady side small birch splits measure 16% pretty consistent at 70dF. The few medium birch splits that ended up on the shady side measure 20% at 70dF and have earned another summer in the sun. All of my split pretty small spruce made it down to 12% in one summer, though some of the splits on the shady side with 180 degrees of bark on them from only being split once hung at 15%. All per electronic gizmo, uncorrected. I have the yellow one with the LED rainbow that says "Blaze King" on the front.
I have a smallish cache, a cord or two, of wood that was split three years ago. It was stored on a porch, about 8' back from the roof line. What happened was a friend of mine sold his house with a wood stove, bought a new house with a pellet stove and let me have his extra dry extra cold winter stash off the porch. I have it on pallets on asphalt and tarped. I brought in close to half a face cord of it, let it warm to 55dF ambient in the garage and found 10-11% ~ ought to be about 12% corrected for temp. These splits were noticeably lighter per apparent volume than the 16% and 20% stuff I handle regularly. I did split two of them open, I did not open them all.
I don't correct for species. My local to me BK dealer is happy and will warranty the cat as long as the electronic gizmo reads 16% or less, corrected for temp but not correcting for species. It might be in the future my local BK dealer is going to be looking for "13%" per gizmo to honor warranties. I don't know, but I intend to be there before he updates his policy. Owners manual for the Ashford 30 calls for 13% or less per electronic gizmo, and it does make a noticeable difference to me compared even to 16% per gizmo.
At my house 20%PG (per gizmo) is usable but needs to be burnt with the stove running wide open hot and makes a lot of ash.
16%MC-PG is good, but burning down the coals and dealing with the ash is a time consuming chore every Saturday.
12%MC-PG birch and spruce is the good stuff.
I am working hard to find nothing wetter than 16% MC PG autumn 2015, I think it's worth it.