The admins here are well aware that, in your example above, Hoya is the name of the genus, australis is the specific epithet, and the scientific name of the species in question is Hoya australis.
The "Add a plant" page uses the term "species" rather than "specific epithet" for one simple reason, it's an attempt to minimize confusion. The average person has no idea what the term specific epithet means. Many people struggle to properly fill out the boxes in the "Add a plant" page as it is, without additional technical jargon.
In your case, we appear to have created confusion by the use of less than precise language. But, there's almost always a trade off between precision and usability, and I'm fairly certain that the use of "species" rather than "specific epithet" has prevented more consternation on the part of members than it has created.
