Make clearer statement about subsets of supported options.

profiles.adoc

@@ -248,6 +248,14 @@ profile, but at the bare minimum tools or runtimes that are claiming
 compatibility with the profile must not report errors or warnings if
 supported options are present.
 
+Proper subsets of a supported option are not a supported option.
+
+NOTE: The profile mandates and supported options describe the set of
+ISA features the software ecosystem for that profile is expected to
+support, as well as the granularity of that support.  Unless
+explicitly listed as a supported option, individual extensions are not
+expected to be supported.
+
 _Unsupported_ _Optional_ _Extensions_ are those that are optional, but
 which are not expected to be generally supported by the software
 ecosystem.
@@ -260,11 +268,6 @@ _Incompatible_ _extensions_ are those that conflict with the base or
 optional extensions.  Software can assume these extensions are not
 present.
 
-The profile mandates and supported options describe the set of ISA
-features the software ecosystem for that profile is expected to
-support, and the granularity of that support (i.e., subsets of a
-supported option are not a supported option).
-
 All components of a ratified profile must themselves have been
 ratified.