Yeah, my bad but the code from grandparent is also incorrect, as for it to be compilable variable must be declared as mutable.
That confused me, as I assumed that code there is compiling. But the only way for it compile is shadowing, so yeah, I kind of assumed that to shadow is to use this syntax. I'm not working with F# for some time, so should've checked before posting.
But I agree with some ad hoc words criticism