> My question is this is this receive exactly the same macro as in SRFI-8?

Yes. `receive` is a simpler version of the standard `let-values`.
`receive` is very popular (https://doc.scheme.org/srfi/support/).

> PS: The other macro that was missing let-optional was not so trivial to
> create, I've got help from Reddit:
>
> https://www.reddit.com/r/scheme/comments/p8ovr7/how_to_define_letoptionals_macro_from_srfi1/
>
> That macro can also be documented, because as you can see from the code it's
> not so simple.

Yes, it's much more complex. One implementation is here:
https://github.com/ashinn/chibi-scheme/blob/master/lib/chibi/optional.scm We
could add it to the Scheme Cookbook.