My mistake: R6RS has `syntax-rules`, not `syntax-case` as far as I can tell. However, `syntax-rules` and `syntax-case` are equivalent in power. [1]
It does not have the same power as `defmacro`: you cannot define general procedural macros with `syntax-rules`, as you are limited to the pattern-matching language to compute over and construct syntax objects.
I think you got your wires crossed. R5 and R7 only have `syntax-rules` macros. R6 has both (`syntax-rule` can be trivially defined as a `syntax-case` macro).
R6 having `syntax-case` macros is one of the more controversial things about it; a surprising number of implementers don't care for them.
It does not have the same power as `defmacro`: you cannot define general procedural macros with `syntax-rules`, as you are limited to the pattern-matching language to compute over and construct syntax objects.
[1]: https://docs.racket-lang.org/reference/stx-patterns.html#%28...