Hi,
You're right I just tested and the modules are not added below the product page. I made a fix and it will be available in next release. In the mean time, you can change the code
$module->setModuleData($this->modules);
to
$this->modules=$module->setModuleData($this->modules);
in the file components/com_hikashop/views/product/view.html.php near line 345
On our demo website we indeed do not use this option. The featured module is used as a standard joomla module and displayed in the bottom position of the template. So it's displayed on all the pages of the website.