Mom had L2-3/L3-4 fusion, laminectomy, rods. She heard from another surgery patient that the 5lb lifting restriction is permanent. True?

Not necessarily. Lumbar fusion patients vary in their activity tolerance after surgery. I allow patients to lift up to 15 lb after surgery. Some have resumed full normal activity in heavy jobs or returned to sports activities including lifting weights. It depends on the patient and their underlying medical problems, their healing, rehabilitation and motivation. It also depends on the advice of the surgeon!! .
Not true typically. It certainly does depend upon the patient and the surgery performed. However, in our practice, we usually limit the patient's to 5-10 pounds lifting restrictions for the first 6-8 weeks, and then slowly progress.