It's a mistake to assert, as you do so confidently, that how functional the language is depends on how similar it is to the lambda calculus. The article agrees

It's a mistake to assert, as you do so confidently, that how functional the language is depends on how similar it is to the lambda calculus. The article agrees with this assertion, Wikipedia agrees with this assertion and I agree with this assertion. Why is it a mistake to assert this? Granted you point to earlier type theory which I was unaware of, but my claim wasn't that lambda calculus was original. If you look at that, you'll discover, for example, that while having functions as first-class citizen was always a definite requirement of functional programming, neither immutable state nor TCO ever were. Here is another big gripe of mine. Given that there are practical reasons for the earlier functional languages to have been different from the lambda calculus (speed and memory), why continue using those languages as metrics later on when the limitations of speed and memory no longer apply?