I don't know about tea and smoking but I am sure of water. Drinking a lot of water before going to toilet enables free and fast flow.
This your question is quite funny. The only way you can verify such claim is to take a survey from those that hold such claim and find out their individual reasons for such claim. When you later start comparing their reasons you would be able to draw a quite reasonable conclusion if it's true or not.
Or you may choose to do the experiment yourself and find out the outcome.
I'm not a smoker, but my father smoked for more than 40 years and said that going to the bathroom smoking was the best thing in the world.
On the other hand, drinking water at room temperature in the morning or a cup of tea helps you start the digestive system and facilitates defecation with comfort. Of both options (smoking or drinking tea) tea is definitely the healthiest.