The rules aren't quite the same for committees and sub-committees. Section 4 of the model standing orders states, amongst other things:
"d The Council may appoint standing committees or other committees as may be necessary, and:
ix. shall determine if the public may participate at a meeting of a committee;
x. shall determine if the public and press are permitted to attend the meetings of a sub-committee and also the advance public notice requirements, if any, required for the meetings of a sub-committee;
xi. shall determine if the public may participate at a meeting of a sub-committee that they are permitted to attend;"
This is why so many councils call their committees sub-committees even though they have no parent committee, as they believe that this gives them the right to exclude the public entirely from their deliberations.