According to the spec:
http://www.xmpp.org/extensions/xep-0124.html#poll
"It may not be possible for a constrained client to either use HTTP Pipelining or open more than one HTTP connection with the connection manager at a time. In this case the client SHOULD inform the connection manager by setting the values of the 'wait' and/or 'hold' attributes in its session creation request to "0", and then "poll" the connection manager at regular intervals throughout the session for stanzas it may have received from the server. Note: Even if the client does not request a polling session then the connection manager MAY require a client to use polling by setting the 'requests' attribute (which specifies the number of simultaneous requests the client may make) of its Session Creation Response to "1", however this is NOT RECOMMENDED."
In other words, the http session should be determined to be a polling session if the wait and or hold attributes are set to '0'. Only at this point should the session be considered a polling one and the polling interval enforced.