I think the problem is using weed means the person is still seeking a buzz rather than learning to live without any kind of buzz.
I know this. One of my best friends detoxed from alcohol repeatedly, never stopped weed, and insisted the weed kept him from drinking. He died from his last alcohol relapse, found two days dead on the living room floor surrounded by empty vodka bottles, his weed and pipe on the coffee table.
I owe my sobriety - from drink and smoke - to his death. Talk about a wake-up call.