"Windshield shops nowadays DO NOT apply sealant to the gasket during installation."
I was told the same thing by the installer from one of the national chains about 10 years ago. That windshield leaked like a sieve, they came back and they did it again.
For a couple of years it appeared that...
Sounds like it wasn't installed correctly: should have adhesive-sealant applied between the glass and the gasket and then between the gasket and the body.