Actually that's not B.S. it is pretty much a standard practice not only with metal detectors but many other products. As a field tester many times you are asked to asked to sign an NDA, Non-Disclosure Agreement which is a legal contract with the manufacturer. It will contain clauses spelling out exactly what you can or can't reveal in testing the product, and if you have any doubts best to check with them.
In the company I work for we use them all the time for field testers of consumer electronics designs of ours. Our field testers are chosen for a variety of reasons with some having the task of testing "the product" against what is currently on the market from our competitors. If those field testers were to break that NDA and begin posting on an internet forum, then it is now lawsuit time.
I routinely sign NDA's for my job and for personal hobby items, and believe that I shouldn't just live by the written page but by the spirit of the document. If one of F75 field testers wants to be BMOC(Big Man on Campus) and starting blabbing to his buddies, then his temperament is not suited to be a field tester.
Now you may think that they should act as self appointed Whistle Blowers, but what they are supposed to be doing is reporting back to the manufacturer to correct any problems so that they are handled before release. Many people want to be field testers because they think it will "be fun", be careful of what you wish for.
Let's take the F75 for instance, a software driven machine with a single button interface. Think about how many mode,tone, notch, disc etc. combinations there are. We're not just talking about a spreadsheet layout with X & Y(columns & rows) we're also talking a very deep Z axis, a three dimensional spreadsheet of software functions that have to be tested. Visualize a three dimensional chess game ala' Star Trek. I wouldn't be surprised if the F75 field testers had a checklist with about 300 combinations they have to test, to say nothing of the operational factors. Interference, ground balance, pinpointing, hot rocks, cold rocks, saltwater, black sand, etc. etc. It can be very tedious, but also rewarding to have some influence on what other hobbyists will have at their disposal because of the field tester's efforts.
Now as to the marketing "obsolete", yeah I think that's over the top, but I also know that's what National Sales Manager types get paid to do no matter what the product, cars, TV's , soup......
HH
BarnacleBill