Hoya cinnamomifolia is now considered a synonym for Hoya macrophylla. Michele Rodda has published a recent paper (2025) that goes into great detail about how a erroneous illustration led to the misidentification of Hoya macrophylla. Here is an abstract from the published paper:

“ABSTRACT. Accurate botanical illustrations play a crucial role in plant identification. Hoya
macrophylla Blume, one of the earliest described species of Hoya R.Br. from Southeast Asia,
and among the earliest to be illustrated, presents significant identification challenges. This
paper elucidates how its first illustration incorporates features characteristic of both Hoya
macrophylla and H. latifolia G.Don, and this is the reason behind the difficult application of
the name. Furthermore, the type specimen of Hoya macrophylla is indistinguishable from H.
cinnamomifolia Hook., a taxon published later and consistently correctly applied. This study
underscores the need for careful re-evaluation of historical illustrations in the context of modern
taxonomic standards. A lectotype and an epitype are designated for Hoya macrophylla and H.
latifolia respectively and their synonyms are clarified and where necessary typified.“