The Psychidae are sorely needing a taxonomist to revise the taxonomic mess that currently exists. This family is one of the least worked and most poorly understood groups globally, never mind in Hong Kong.
There are a host of mis-identifications online, as well as in published literature, so making any headway is difficult without access to fully worked material (kept in the major institution collections). Full documentation of life histories and resulting adults is needed to tackle this situation, and in HK the work has not properly started at all. All I can say about the genus Eumeta is that it is applied too broadly, with only two species actually valid - minuscula and variegata; as specified by Robinson, Tuck and Shaffer, 1994: Smaller Moths of Sout-East Asia, and both of which have a mass of synonyms.