"AN" is a quality standard. This supplier is advertising product as AN, without meeting the standard. It is a fraudulent claim.
Interesting; I take it you've verified their components don't meet the standard? Or are you just stating your opinion as fact? In reality, you may be right, but there is a big difference between supposition and fact, and what you're doing is impuning a vendor without any data provided. And who says you need to meet an AN standard anyway?
This all comes back to using the right standard for the application. Using 3,000 psi tested stainless braided hoses that were manufactured to a military standard will do the job on my RV-12 brakes, but so will parker plastic hoses with brass compression fittings (that are amazingly similar to the ice maker hose installation on my frig).
Referring to Captain Avgas's story; I'm glad he was able to find a problem and repair it. I have a different story with involves Earl's hoses and fittings on my '69 Mustang. I replaced all of the brakes with {gulp!}
reinforced rubber hoses about 20+ years ago - Earl's (now owned by Holley) has been in the business a long time, which says something about their quality. That was the standard for automotive brakes at that time and they still work very well. I purchased, assembled and installed them myself. And before you say "that's a car, this is an airplane", note that the braking service duty of a 2 ton car is much greater than my 750 pound RV-12.
Additionally, noting that the vast majority of failures are human error, when I hear that some product leaks - or failed, my first question is to the assembly of it. The key is to use the right component (standard) for the right service use (application) and then assemble and install it correctly. A high quality hose installed incorrectly is worse than an "AN Fitting From the Internet" hose that was installed right.
I noted that this thread has been viewed almost 3,000 times, yet only a handful of folks have participated in it. My
guess is that there are many positive stories about amateur assembled hoses, but those stories are unheard due to reasons that probably include fear of rejection by a few folks on this forum that have very strong opinions. I hope for a more inclusive builder forum that welcomes diverse perspectives. I believe in having an open mind, just not so far open my brains fall out.
There's nothing wrong with failing at an experiment, so I encourage folks to try things - using good engineering practices (if you lack GEP, then please do seek assistance from the fine folks advertising here...). Note that I'm not encouraging someone to make something, install it on your airplane, load up your family and launch off into the clag. There is a substantial difference between my experimental airplanes and my Beechcraft Baron; and anyone who believes their experimental airplane meets or exceeds the certification requirements of FAR 23 is misguided - that is unless you have the certification and testing documents, and you use a certified A&P for your maintenance along with an IA for your annual inspections and major modifications. This is a silly concept. However, do use the best you believe you need, just don't think everyone has to do it your way. That is the entire value and beauty of E-AB, a category I hope does not go away.
And whether certified or not, or whether it was manufactured to a specific standard or you formed it from raw materials into a product YOU designed, any maintenance performed on airplane needs a post maintenance evaluation. Ground run the engine, take a test flight around the field where you can land if the engine quits, fly it for a defined period of time with a good test plan - evaluate the result and make changes if needed. But DO participate in amateur building.