Hi, yes only applies to eBay store inventory items the URL for the info on eBay is :-
http://pages.ebay.com/help/specialtysites/referral-credit-faq.html
where they say :-
"The item sold must be in Store Inventory format
Sales of auction-style and regular Fixed Price format items will not earn Store Referral Credits, even though these items appear in your Store."
and they have tight requirements on how direct someone lands on your store too