Looking at JQuery Mobile 1.3.2 as opposed to 1.3.0-beta.1 it appears this part of the documentation has been removed.
They removed support for having multiple panels opened at once.
This is how I solved it.
//Overrides JQM's default behaviour of having a single modal panel, and instead bases modality on position.
self.overrideModalPanels = function () {
//remove all panelbeforeopen subscriptions (jquery 1.3.2 source looks like it only uses this to handle panel modality.
//may change to document on jquery 1.4, check against https://github.com/jquery/jquery-mobile/blob/1.4-stable/js/widgets/panel.js#L260 but on master for versions past 1.4
//ctrl+f panelbeforeopen
//$(document).unbind("panelbeforeopen"); //jquery 1.4
var page = $('#idofpanel').closest(":jqmData(role='page')");
page.unbind("panelbeforeopen");
var panels = $(":jqmData(role='panel')");
panels.each(function (index, element) {
// Close the panel if another panel on the page opens
page.on("panelbeforeopen", function (e) {
var position = $(element).jqmData("position");
position = position ? position : "left";
var position2 = $(e.target).jqmData("position");
position2 = position2 ? position2 : "left";
var positionsMatch = position === position2;
//if positions are the same, and there is a panel already open, that isn't the one opening now.
if (positionsMatch && $(element).hasClass("ui-panel-open") && (e.target !== element)) { //roughly equivalent to if ( self._open && e.target !== self.element[ 0 ] ) {
$(element).panel("close");
}
});
});