That may have been true ten or twenty years ago.
In reality there is no difference nowadays, and certainly no emulsifiers added to yoghurt.
It's just made with skimmed milk.
If you make yogurt it’s all just milk and good bacteria. However that is not what is sold in the shops mostly. Lots of stuff beyond the yogurt and fruit, including added starches along with vague “flavourings” and odd colouring sources. The (unflavoured) Greek style ones do seem to be just the yogurt
Tesco (creamfield) berry medley low fat yoghurt
Low Fat Yogurt (Milk), Cherry (8%),
Sugar, Cherry Juice from Concentrate (4%),
Modified Maize Starch, Lemon Juice from Concentrate,
Potato Starch, Flavourings,
Gelling Agent (Pectin).
Ski smooth strawberry and raspberry low fat yoghurt
Strawberry: Low Fat Yogurt (from Milk),
Sugar, Strawberry Puree from Concentrate (2.5%),
Rice Starch, Natural Flavouring, Concentrated Lemon Juice, Beetroot Red Concentrate,
Thickener (Guar Gum), Raspberry: Low Fat Yogurt (from Milk),
Sugar, Raspberry Puree from Concentrate (2.5%),
Rice Starch, Beetroot Red Concentrate, Concentrated Lemon Juice, Natural Flavouring,
Thickener (Guar Gum)
Muller light red fruit fat free yogurt
Yogurt (Milk), Cherries (10%), Water,
Modified Maize Starch, Flavourings, Colouring Foods: Carrot & Pumpkin Extracts, Beetroot Juice Concentrate, Black Carrot Concentrate, Acidity Regulator: Citric Acid,
Sweetener: Aspartame