That's the intended behavior of the destroy method.
You can add your own destroy method which doesn't call kendo.destroy()
(which is responsible for destroying the child widgets) and call that instead:
kendo.ui.Splitter.fn.destroyNonRecursive = function() {
Widget.fn.destroy.call(this);
this._detachEvents();
if (this.resizing) {
this.resizing.destroy();
}
}