How does someone abuse price matching if they are following the policy of the store? A store offers it in order to get some customers to do all their shopping there rather than elsewhere.
It isn't like someone is abusing a return policy and making a fraudulent or no receipt return of items bought elsewhere.
The store is completely within their rights to modify their policy (as they have done here). Some shoppers won't care and others will. However, if a store offers something and customers use it as per the policy of the store, it isn't abuse.
Never say never