There is no universal "country of origin" filter. Some sellers may include a "country of origin" item-specific, but it is not a requirement and eBay does not verify information provided by sellers even if it does appear.
If large numbers of buyers use that item-specific or the "item location" to filter out certain countries, you can be sure that some sellers selling items from those countries will not include that information in their listings if they think it will affect their sales, or will ship the item elsewhere to sell, or may even mislead about actual item locations.
The cost of return shipping to this certain country is always more than the entire purchase price to begin with.
If an item is not as described, the seller is responsible for paying for return shipping; if the seller does not cooperate, the buyer can get a refund without a return.
Even in cases of buyer remorse, the buyer is only responsible for returning the item to the location specified in the listing. A seller cannot claim that an item is in one location, but then require a return to another location at the buyer's expense, otherwise a seller could avoid any refund by making returning the item to Mars a precondition (and there are definitely sellers that would try that if they thought they could get away with it).
Use the information that sellers do provide (or the lack of important information that should appear but that is obviously missing) in order to choose your sellers wisely and you may be able to avoid many sellers that are directly selling those inferior items or the sellers that purchase such items to sell to others.
