Individual Variation products show as individual listings because of the way that Trade Me have structured Multi-Variation listings. 

To buyers in Trade Me your Multi-Variation listings will appear to be a single listing, but each product on the Multi-Variation listing has its own listing id and listing within your Trade Me account. e.g. if your Multi-Variation listing has 6 variations then 6 listings will be created, one for each variation. The listing displayed depends on the buyers selection and the buyer will appear to seamlessly stay on the Multi-Variation listing with each selection.