I have no clue how it was decided to call it "steeping"...Steeping is a process in which essential oils and/or flavors are extracted in a liquid, usually water, such as tea. Tea leaves are saturated in hot water to extract the oils into the liquid (water). There is no extraction going on in e liquids. All the ingredients are simply mixed together following a recipe for the desired result. The only extraction going on is when tobacco is used as the base flavor, also called maceration to be more precise where tobacco sits in the liquid for a given time frame to allow the oils to "steep" into the liquid.
Now the more appropriate terminology should be "aging" where all the ingredients are mixed together and allowed to sit for a period of time to allow them to mature or "age". This usually makes the liquid have all the flavors "come together" as one to achieve the full richness in flavor.
There are some e liquid flavors that are alcohol based, such as in a vanilla extract and allowing such liquid time for the alcohol to evaporate and leave only the flavoring remaining in the liquid is really what is going on. There is also time needed to emulsify liquids to achieve the desired result, stirring and shaking aid in this.
But in no way is any of this known as "steeping"...unless you have a tea bag in your juice!
