Ordinarily when creating a cultivar, the proper procedure is to document what you did to created the hybrid. The seedlings should be grown out and the the one that shows the greatest vigor and desirable traits is kept, and all of the other seedlings are culled. The plant that is chosen is then named and generally registered with the proper international society. Apparently this society does not exist for Hoyas strangely enough. Please correct me if I am wrong here, but according to the information that I found online there is no international cultivar registration authority for Hoyas.
The plant that is registered and named then becomes the plant which is propagated from cuttings and only that plant can be considered the named cultivar.