Cellarmasters is a Woolworths company, and these are some documented Woolworths (and Coles, and Aldi, and …) labels. Some labels are vineyards but others are just labels on mass produced wines. Many are also featured at other popular Woolworths outlets like Dan Murphy’s or BWS. Cellarmasters have packed their ‘Woolworths Shareholders’ offers with their house labels and those house labelled bottles have been very good to excellent for the most part but as you wrote, regional variety can be hit and miss (and loaded with house labels making knowledgeable selections opaque).
Another Cellarmaster feature is that if you don’t buy for a while the $25 voucher will become a $50 voucher