Does the dish lose flavor when it releases a lot of smell?
No, not really. Yes in another way.

Scent is a great indicator that you have achieved your objective. Recipes will often say things like "sauté until aromatic". With experience, bakers can often tell that bread is done by the smell. Things simply smell done. If you stop cooking before you can smell that doneness, it is likely that you will miss out on what that dish could be. 

You are correct in that every molecule your nose picks up without the palate is one that your palate cannot experience. But once your nose is really tickled by the aroma, that is a strong indicator that your food is ready to release those flavorful molecules in a way that our palates (along with our noses) can interpret.