OK, I got it wrong (as usual). However, I'm not sure about the answer.
Please, correct me if I'm wrong:
There is no thing such as an IP_ANY port.
The Well Known Ports are those from 0 through 1023.
The Registered Ports are those from 1024 through 49151.
The Dynamic and/or Private Ports are those from 49152 through 65535.
SOURCE: http://www.iana.org Port Numbers
IP_ANY seems to have been used in that BOL page to indicate that the SQL Browser service is not cluster-aware, so it listens on all IP addresses. However, the port it listens on is always UPD 1434.
This behaviour of the SQL Browser service is well known and documented (I had to fight with it some years ago) and it can cause some head-scratching to network admins. When it receives a request on a virtual IP address, the SQL Browser service can send the response datagram from any of the IP addresses of the server machine, which causes many firewalls to drop the datagram. You can see this happening using Wireshark or Netmon to sniff the packets.
You can read more here: Unable to connect to a SQL Server named instance on a cluster
and here: Unexpected Behavior Setting Up Firewall Rules with Clustered SQL Server Instances
I don't give a damn about the points, I just want to make sure I understand things correctly. 🙂