No, of course not. Factorial are just an illustrative example.
My goal was to dispel the myth that the lamdba calculus is nothing more than an intellectual curiosity. It is much, much more than that, not because you can use it to compute factorials, but because the techniques that you use to compute factorials in LC are generally applicable. If you really want to master the craft there are a few things you really need to know how to do: write your own compiler, your own editor, your own implementation of the Hindley-Milner type system. Writing an efficient factorial in LC is like that. It's not useful in and of itself, but for what you learn simply by going through the process.
Your initial words were "Here is how you can use the lambda calculus to compute factorials in non-geological time" which led me to believe you were claiming LC was a very (the most?) efficient route to factorial calculation. Which would make me sit up and take notice were that the case.
I'm sorry to say that your factorial example just seems painful and pointless to me, and doesn't encourage me to expand my mind via LC at all.
> LC was a very (the most?) efficient route to factorial calculation
It is, because it is a standard model for computation. To put it in layman terms, every programming language is lambda calculus in disguise. You have absolutely no idea of computability theory. That is the theory in which the P=NP conjecture is formulated, which has massive implications e.g. on cryptography.
You seem frustrated for not understanding at all what's going on here and you try to provoke answers. I know what I'm talking about, because I don't grok LC either and I get furious quickly when I'm hungry, tired or overworked. You are paranoid.
My goal was to dispel the myth that the lamdba calculus is nothing more than an intellectual curiosity. It is much, much more than that, not because you can use it to compute factorials, but because the techniques that you use to compute factorials in LC are generally applicable. If you really want to master the craft there are a few things you really need to know how to do: write your own compiler, your own editor, your own implementation of the Hindley-Milner type system. Writing an efficient factorial in LC is like that. It's not useful in and of itself, but for what you learn simply by going through the process.