It doesn't support continuations, TCO, and libraries, but it support
everything else from R5RS and a lot of R7RS (some functions need upgrade
to include multiple arguments that were not in R5RS). It should at least be
marked as "partial support". I know that TCO is fundamental for Scheme, but
the same is syntax-rules that not all implementation have.
But if you decide that it should be marked as "not supported" or something
similar, I think it would be better than not being included.
I would like to include it. I want to be supportive of all implementations of Scheme and variants. We should encourage anyone who is putting in the work to implement and maintain a Scheme or Scheme-like implementation. At the same time, we should make sure that visitors know what they're getting into before investing effort in a particular implementation. For many purposes, full compatibility isn't important, but it's best to know in advance.