It's one of those "different strokes for different brewers" things. Really it is whatever works for you. I usually use hot water myself. The point is to let it steep for at least 1/2 hour and to not exceed 170 degrees or else you will extract tannins...
The instructions for recipes are usually written in terms of the author's brewing style/preference. if they were a hot tap water steeper, then the recipe would probably reflect that.
Some people even cold steep overnight.
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