Very odd that the rim has ERD printed on it, and that it calls itself 26 x anything. Perhaps this is some confusion cause by 27.5 actually being the same bead seat diameter as old 650B, which used to be called 26x1-1/2. Hard to tell, though. THat size is not referred to as 26 x anything in this day and age.

Anyhoo, the second complicating factor is OP's insistence on measuring parts in inches then trying to shoehorn this measurement into the names of tire sizes.

NB. Tires size names are generally indicative of the nominal diameter of the wheel with some arbitrary size of tire mounted. All of these sizes pre-date fat and + bikes, so a 27.5" named wheel with a fat or + size tire will not be anywhere near 27.5".

Measuring the diameter of the outside edge of the rim is pointless.