Well, you've done nothing to prove that this is a less efficient way to drive a LED from an AC power line than some other way. I'd go so far as to say that it's probably more efficient than using any kind of "LED driver" (meaning some sort of converter, like a buck converter), since all those have some losses (small, but not zero).
Notice I didn't say "safer", or even "better". The current topic is efficiency.
I'm always ready to be convinced otherwise, but I'd need some proof. Claiming that one should do things "by the book" is not a convincing argument, in and of itself.
Don't worry; I take no offense at your comments. You do seem, though, to be taking quite an orthodox approach here, with not much supporting evidence.