Just starting to get into yeast management and in every instance I can find describing how to rinse yeast people are boiling water, letting it cool and continuing from there. What would be the difference if I were using a store bought gallon and sanitized jars?
The primary intent of boiling the water is to kill any bacteria or other critters that may be living in it.
If you are confident that the water you buy at the store is of the same purity, then by all means use it. If not, then you should boil the water regardless of source.