Can you cite the article where it says you can express nutritional data with respect to a final form of the product you mix yourself and not list the per 100g/100ml data? I'm still very skeptic but would be quite interesting if that was really allowed.
Ive found mentions of it here: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A...
From Article 31: "Where appropriate, the information may relate to the food after preparation, provided that sufficiently detailed preparation instructions are given and the information relates to the food as prepared for consumption."
I'm quite surprised as it adds ambiguity and complexity and leaves a backdoor open for playing with serving sizes and dilutions. I mean they could list the instructions for a diluted final product that makes the values look good but the actual preparation everyone does is way more concentrated.
Fortunately it doesn't seem that exploited if not for very specific products.
You're correct that the requirement is for 100g/100ml "as sold" not "as prepared". The other commenter is incorrect.
So milk powder, for example, would have a mandatory nutrition label showing 100g of powder and then the company can optionally add a second label showing nutrition for a serving of prepared liquid milk.
Since most companies add whatever serving makes it look best it becomes habitual to filter out the serving size info.
If anyone wants to dive further into this it's EU regulation 1169/2011 Annex 1.