Only because there's a property and a method somewhere in Openfire doesn't mean the exact same syntax can be found in the XMPP specification and can therefore be used for the muc#roomconfig_ fields.
I suggest you inspect the possible values for muc#roomconfig_whois. Maybe it has "none" value?
The spec says:
Note: The _whois configuration option specifies whether the room is non-anonymous (a value of "anyone"), semi-anonymous (a value of "moderators"), or fully anonmyous (a value of "none", not shown here).