What is a Field Blend? The varieties of vines e.g. Cabernet are propagated by cuttings so they are all identical. Back in time vines were crosses from pollination thus each plant was different. Also vineyards were often planted with many varieties. Hence the Field Blend being a wine made from all the different clones and varieties in the vineyard.
Recall the overall flavour is controlled by the weather of each vintage. There are many varieties and several vintages making this wine though you will detect Shiraz and Durif, favourites of Glug while the components are from several recent vintages.