This seems to be a never ending subject, I have been working around aircraft for 40 years and have always used fuel lube on pipe threads. This was from instruction by my first boss who was an experienced and military trained AME, A&P. I learned years ago that you do not put aluminum pipe fittings together dry unless you want to order new fittings. I feel that most times pipe fittings leak they are not installed tight/deep enough. I also think that pipe fittings seal because of their design, taper, and not because they have a compound of some sort applied. The reason for applying fuel lube, EZ seal or whatever you choose is to lubricate the thread and allow it to go together further and tighten/seal deeper into the taper.