"bloke's got a screw missing"
What an insensitive and judgemental thing to say.
I would be interested to see any medical qualifications held by the person who posted that opinion.
Maybe the patient has psychological issues - maybe he just "made up" the 3/4 cups per hour of tea and all the other beverages he claims to drink. Would there be enough minutes in an hour and hours in the day for him to actually drink what he claims to drink?
It is possible that the GP was aware that the man has psychological issues and was putting his mind at rest to try to ease his distress. That is most certainly not a waste of time.
Let's hope that those people who would dismiss this man as "having a screw missing" never themselves suffer from any form of psychological problems. But if they do, I sincerely hope that you are never dismissed as "having a screw missing".