The cause was so simple, answer points just got thrown away :)
The CSS selector included [data-ios="true"], as that was the styling from the Brian Dadaway control, but the "data-ios" attribute was missing in mine as I wrote it from scratch.
The fix in code was to add
if (navigator.userAgent.match(/ipad|iphone|ipod/gi))
{
THIS.$wrapper.addClass("ios");
}
and change the css to:
.groupList-Wrapper.ios .groupList-Header.groupList-Fake
{
right: 0; /* no scrollbars in iOS devices */
}