you can assume that there are a lot, and not only those from the back surgery.
An overweight smoker aged 64 (probably not good physical condition) likely also has high blood pressure, high cholesterol, possibly diabetes and pulmonary problems.
You definitely need to obtain a physician’s approval to exercise. If you get that, I would follow the advice on the form and contact the physical therapist who the client saw and get more information there.
It is certainly a scenario where you need to proceed with caution.