Wow, you weren't kidding about this one being hard to find info on. The taxonomy appears to be very confusing. Both Dendrobium sociale and its accepted synonym, Den batakense, are listed in the Kew list, but both listings say that they are synonyms for Den metrium?!?
(see below)
World Checklist of Selected Plant Families: Royal Botanic Gardens, Kew
Anyway, the Orchids Wiki says:
Dendrobium sociale - Orchids Wiki
IOSPE says it is from section Grastidium, and the book I have on Dendrobiums confirms what IOSPE says about location and having stem-like pseudobulbs. It says section Grastidium usually grow in areas which have rainfall all year. It says the flowers last only a day and this is why they are not commonly grown by hobbyists, and also why there are problems with the taxonomy. Most or the plants listed under this section in the book say watering is required year-round. A few require a slight drying out between waterings in winter, but it doesn't seem like any of them require a proper winter rest.
Please note, I am not an expert! This is just the information I've found.