Me too. It's been fun so far - smoking cigars for science. Now my wife has less cause to gripe about this hobby.
Question for you or anyone on here who knows. So the moisture meter I am using has two settings: Wood and building materials. Dry wall I'm thinking. I just tested a stick that has leveled out in my 69% box and it read 18.2% for "wood" and 2% less for the other. (It had clear burn and taste issues to summarize my finding on that one) Which setting do you think more closely represents tobacco leaf? I'm leaning towards the smaller reading simply because 13% is supposedly the general rule of thumb for cigars (according to that fancy humidor company who's name escapes me at the moment).
Obviously if something like this were to ever actually be developed and marketed, the electronics portion would have to be calibrated for "tobacco" whatever that setting ends up being.
The short answer is "it doesn't matter". The reading you are getting is just a number that "represents" the cigar moisture content.
A bit of background.... different types of wood have different properties. Oak is different than pine, etc. Even different species within a group, such as Yellow Pine, Scots Pine, Red Pine, all have different properties which affect the moisture meter readings. A good moisture meter will have the ability to be programmed to the specific species of wood being tested or have a conversion chart that tells you what to add or subtract from the reading to get an accurate reading. These differences between species are usually only plus or minus a couple of percent. Cheap meters don't have any correction for different species so your reading is always "close" but may be off by a couple of percent. This is OK because most people use moisture meters to see if wood has reached an equilibrium with the surroundings or to monitor it as it dries. The exact % is not critical.
The meter you have can be switched to "building materials" . The same holds true for building materials. They are not the same. Drywall is not the same as carpet or insulation. The readings will simply be "relative", meaning you can see if something is wet or dry or if something is wetter that something else.
So what does all this mean.... If you want to convert the meter reading to the actual moisture content of the cigar then you have to do the "oven-dry weight" calculation that I talked about previously. Then you will know what 13% on the meter actually is in % moisture in the cigar. If you just want to know what is the optimal reading for smoking then you can just do what you are doing now.
My suggestion is after you finish your tests you should relabel the moisture meter with colors, red-yellow-green-yellow-red. The red is too wet, yellow is a bit wet- green is good, yellow is a bit dry, red is too dry, or something like that.
Sorry for the long post. I hope it makes sense. This may be better explained if you google "moisture content in wood".
It may be just you and I who are interested in this.