I can't see how the water heater can explain stink in the cold water, unless your plumbing is run in a way where thermal expansion in heater can drive water backward into the cold piping.
Do this: Get water heater up to temp. Draw some cold and check for stink. Then run a few gallons through cold, then draw another glass and check for stink. If the second glass has stink, sounds like your fresh water tank has the skunk and water heater is not responsible.
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