'Steeping' means to age and mingle to me
Steeping, like many things here, is all down to personal taste. I haven't found many shop bought juices that need to be steeped but if something had been out of stock just before it arrived then I do tend to just let it sit in the dark, with the cap on for about a week just giving it a good shake everyday.
I find steeping is a nesseccary step though when dealing with DIY juices, even if it is just a case of mixing shop made juices, it allows for all the flavours to completely mingle together and they will taste fuller.
There is no right or wrong way to 'steep' a
juice either, everyone finds a method that suits them and their juice best.