washing machine hookup to cold water - where?

[Laura Turner]

I had a plumber run plumbing for a washing machine.  He hooked up the supply lines about 7 inches above the water heater in the basement - hot water ties in 7" above water heater output, and cold water supply ties in about 7" above the intake to the water heater.

Now, when I turn on my kitchen faucet directly above the water heater, the cold water runs hot for a few seconds before it turns cold.  The plumber says that's because I'm getting the 7 inches of heated water  between the water heater and the cold water line.    Which I guess makes sense ... but if that's the case, why didn't the cold water run hot for a few seconds before that?  Why have I never in my life noticed this issue from any faucet in my house, a public bathroom, etc? 

Is it ok for him to have tied in the water there?  Or should he have tied in somewhere else?

Thank you.