Gentelmen, a merchant would describe the adapter in order to sell it. So I guess it depends on one's perspective
Thank you!!! That described the answer AND the reason.
My first experiences in RF/microwave connectors were as a grad student. We used HP Vector Network Analyzers to measure various types of dielectric materials - this was a med school application, so we were not RF engineers but rather med school students who needed to use materials analysis for our work.
The HP network analyzer people were insistent that when they said to "use a male calibration standard", they did not mean a 50 ohm resistor on a male connector...it meant a 50 ohm resistor on a female connector, to mate with the male test port on the instrument. When adapters were needed, they were described similarly - by which connectors you need to hook together. But...HP was the user of the device, not the vendor. The vendor, naturally, can only look at the adapter he's holding in his hand, and naturally that is what he would describe.
My local hardware store does sell 3/4" drill bits for wood and steel. The difference was described to me: the wood-boring bit is cut differently to cut wood and is also made a little larger that 3/4" diameter, so that the final hole in the wood will be 3/4". The metal bit does not have to be oversized, because metal-cutting bits, due to chips, end up making a hole slightly larger than the bit. So, the metal-cutting bit is in fact, a tad undersized.
Nominal dimensions for things all make sense, but only if you know the real explanation, which is hard to get sometimes. Why is a 3/4" copper water pipe closer to 1"? Someone told me once, it had something to do with being able to fit into the same fixtures as old-fashioned 3/4" galvanized steel pipe, which has thicker walls. Why are 2 X 4s smaller? Kiln drying, I suppose.
I assumed there'd be some similar reason why, when adapting two things together, you didn't actually indicate the application...and in this case it's simple motivated self-interest on the part of the vendor.