As for https://r7rs.org/, it is hosted by the R7-large working group. It
duplicates a bunch of the stuff on scheme.org. I don't know why, but it
is normal in Scheme that groups keep their distance from each other and
duplicate work. It calls for a lot of patience from all concerned. Every
project to bring the community together has a deep political dimension.

https://prescheme.org/ similarly could be under scheme.org but it's
entirely separate with no communication.

Lisp is a very long-term project. I don't expect Scheme.org to be an
obvious success until its 10th birthday. YMMV.