Limit to the number of Rules for a Local Traffic Policy

When your client connects the routing decision on the pool member is made at the start of the connection. Subsequent requests sent down that TCP connection will always go to the same pool member thereafter, regardless of what is written in your iRule. It only uses the pool selection at the start.

When you type that into the browser box and hit enter it is sending the request down the same connection. So it goes to the pool member that has already been selected for this connection. If you waited five minutes it would route correctly as it would be a new connection.

To change this behaviour you need to use a oneconnect profile on your virtual server. This means the pool selection can be evaluated on every single http request.