Those never worked right, which is what led to newer innovations. The Kayfun with a basic micro-coil and cotton build is pure genius and just works.
Will that stop others from experimenting and coming up with better solutions? No.. it won't.
When you look at the basic premise of "learn to walk, before you run", that advice makes perfect sense. It's just folks jumping the gun and attempting dual, quad, mundys magic etc etc before they can figure out a basic coil setup 100% of the time, that this advice does not apply to. Example: I would not ask a user with a single KFL to experiment with their juice feed channels or air intake port. If they mess it up, they are without a resource to fall back on. If you have two or three, go ahead and experiment all you want, because you can always fall back on your spares in the event of a mess up.
I think that the advice is sound, in principal. It's good to have a solid back-up plan and then allow room for experimentation for future innovation.