In most countries, ingredients have to be listed. Are there any additives listed where you are? There aren't in the UK.
The sweetness of milk (lactose) is soluble in water and not in fat, so removing the fat won't remove lactose. In fact it will slightly increase the concentration. Whole milk has 3.7 g fat and 4.7 g sugars per 100 ml; skimmed milk has <0.5 g fat and 5.0 g sugars. Replacing the lost fat. Within rounding error the extra sugar is accounted for by replacing the fat with more of the non-fat components of milk.
If the manufacturers were going to add stuff to make it more like whole milk, you'd think they'd do a better job of it. I normally have semi skimmed on cereal and to make hot chocolate, and the difference between that and either whole (rich) or skimmed (watery) is significant.
When you come to processed dairy products it's a different story, and this may be the source of someone's confusion. Fruit yoghurts take this to extremes, as fat-free versions are more likely to include thickeners (typically corn starch or pectin, so nothing unusual) and "light" versions have sweeteners, water, flavourings, and in this particular example gelatine.
This is also the case in the Guardian article you link - the relevant quote is
Often, flavorings such as chocolate and strawberry and sugars are added to low-fat and skim milk to make up for the loss of taste when the fat is removed
which is pretty clearly referring to milk-based drinks and not to milk (it goes on to mention added sugar). So the article isn't (necessarily) wrong, but isn't particularly useful.
As for recipes, most specify, if they don't, use whatever you have anyway/prefer. Preferences vary with time and place; many years ago the only way to get skimmed milk was to skim it yourself, probably to use the cream for something.
