Matching Client IP to Network List in Data Group

I have this requirement to decide if the client IP address is in a list of IP networks. The IP networks are in a Data Group. This is the IF statement:

if { not ([ class match [IP::remote_addr] equals address_group ]) } {
  log local0. "Client [IP::remote_addr] not in address_group"
}

This is a portion of the class definition:

class address_group {
   {
      network 10.0.0.0/8
      network 172.16.0.0/12
    }
}

To my surprise, the log statement triggers on a client whose address is in a the 172.22.104.0/21 subnet. How could I modify the IF condition to handle this case, or does this seem like a bug?