According to the 7th edition of the Publication Manual, the retrieval date for online sources is only mentioned if it is likely that the content of the webpage will be changed (e.g. a Wikipedia entry, social media).
Because it is not always clear whether a web page could change, the Dutch APA Working Group recommends to include a retrieval date for all online sources, except for publications with a DOI link or publications from unique databases such as Nexis Uni.