Turning off cache in remap rule has unexpected Proxying cases

We are using
@plugin=conf_remap.so @pparam=proxy.config.http.cache.http=0
in a remap rule.

We see 2 unexpected proxying cases:
1) Cache-control: only-if-cached.
Normally a request with this header will only return a 200 if the object is cached (504 if not cached). We always get a 200 OK for these urls, suggesting the request is forwarded to the origin. (If the X-Debug plugin is installed, and X-Debug:X-Cache is also sent, the response indicates the cache was skipped.

2) PURGE.
When we issue a PURGE request for urls matching this remap, it appears that the PURGE is proxied to the origin server.