No, V9.1 does not support Sophos on a MAC, the support is for some other function but not anti-virus. I was hoping that the free version for a MAC might be supported in this release, but no.
The Mac support you see in the release notes is for the Sophos Authentication Agent, not the Endpoint Protection -- I too was expecting Mac support in the Endpoint Protection feature in 9.100, guess it didn't make it in.