In door air testing is a good primer before heading outside for a field hunt. A whole lot better than just going outside without any knowledge how a detector could and would respond to a particular target. Plus you get a better understanding on using the control functions. Sure cuts down on learning time and frustration especially for newbies. Better than just reading the manual, taking the manual with you and reading as you hunt figuring out a detector.
Plus the lack of detecting weather, it is winter up here in the great white north. You can either sit there looking at the detector waiting for good weather or you can turn it on and play around and make yourself useful.
There was a time when manufacturers included in the owners manual a section on "Bench Testing".......................
So in other words, you don't care what happens on the bench? No use to you? You would only like dig results? I like to know and learn what owners of machines learned in operating a machine, it helps me being more proficient in using the same machine. Finds don't tell me much more than the detector can find items. I want to know, how and why..........
There was a time before the internet, you bought a detector and you had to figure it out. You only had magazines with tests and possibly lucky enough to have a friend or fellow club member with the same detector who would share his knowledge. Just be lucky you live in the internet world where you can learn a ton and there's people would will help in teaching you to be a better detectorist.
As for being fair to Nokta/Makro? Everyone knows a bench air test cannot fully indicate the true performance as with actually hunting in the ground. In mild Florida sand, the Simplex according to NASA Tom, depth is exceptionally deep. The magnetic dirt sand mix we have here in Canada can put the hurt on a detectors performance drastically. On average here, our soils you can expect a 25-40% decrease from air test results. From an air test, you can determine approx. performance before you even get out in the field. So again I find air testing useful and so do many others.