C7Z Fuel Smell on Cold Start

I had my fuel pump assembly addressed half a year ago through Chevy’s extended fuel pump warranty, and the gas smell has come back. It happens on cold starts and I explained that to the service advisor when I had dropped the car off for a diagnostic of the fuel system+oil change. They visually inspected the lines and fuel pump and could not replicate the issue, so they did not perform a smoke test and didn’t charge me for the inspection of the lines or pump. My question is why they’d not perform a smoke test anyway seeing as the issue only happens on cold starts? Anyone else have this issue reoccurring after their warranty “fix”?

Thanks in advance!