Yes I see where you are coming from, even if you dry during the summer your logs would gain moisture prior to sale in winter, BigJ said much the same with Scotland. Comparing a few dates in Summer my location has RH some 30%age points lower than yours.
The other salient point is that even if the equilibrium moisture content indicates 20% with RH of 90% if the log is above 20% it will hardly be losing any water.
I wonder how they derived the figure of 20%, it may have come from stoves manufacturers testing their offerings with wood at that mc.
I've pointed out in the past that the water content of wood doesn't affect the energy content much but it does affect the completeness of combustion IF the firebox loses too much heat. Stubby recently said his stove had a double glazed door in order to maintain a high firebox temperature, so in the right stove there is no reason a high water content cannot be burned cleanly but in a simple metal box it may well be that 20% is needed.
Your protimeter tells the story but it would be interesting to run an experiment with Lascar temperature and RH loggers in one of your covered loads and a similar one under a cover with no drying logs in parallel plus sample weigh both a log being dried from green and a bone dry log over a full year in your conditions.
The paper also states that air seasoned wood needs 2 years (which I read as 2 summer seasons as little drying occurs October to April). I cut my own logs (from timber mostly care of Jonny Burch this year) and have no space to store 2 years worth under cover. Though I have shown I can get individual logs down to below 20% in a couple of summer months I know conditions are not that favourable in my stack and hence probably burn some logs at 30% or more if that bit of the stack has poor air flow. As my Jotul 602 is just a simple metal box I intend to upgrade to an "ecodesign" stove with an insulated firebox but have yet to find anything that sits in my fireplace with plenty of room at the sides and back like the Jotul does.
I see, but you are still not addressing my point of the interpretation of 2m3, whether it means solid wood or a bulk volume.
BTW with your approach to your firewood I'm confident in your furniture making skills should you revert to your old trade.
As a naughty aside, I worked with an old lag who would buy a fine piece of antique furniture and strip it down to its parts, he would replicate all the parts and reassemble two pieces each with half new parts and half old and pass them off as the original genuine number. It was a shame he (and his boss) were so greedy as he was genuinely skilled and knowledgeable about antiques.