Yes, part of the purpose of steeping is to let the flavors blend and meld into a single, unified flavor. A single flavor can need steeping, especially if the "Peach" is created with more than one peach flavoring. Oxidation is also a part of steeping, which is one reason to steep part of the time with the cap off. A small amount of evaporation will happen, but if you look at the 15ml bottle you will notice that the neck is small enough that your juice will not evaporate away.
There are different steeping methods and people who swear by each of them. Almost all of them involve 3 things: time, shaking/mixing, and oxidation.