It is rather odd he at least once pulls down his mask to wave at people, maybe give everyone a big smile of thanks for their support.  Like you said it could be a set up.  On the other hand you'd be amazed what people on oxygen can do.  Like you'd think my brother, before he finally passed, couldn't pull two oxygen loaded carts and go down and party with the homeless at the river all day, come back drunk and all belligerent but he would.  They gave him three years to live and he made it five.  Partying the whole time.  Requires oxygen still doesn't necessarily mean 24/7, that was the case with my brother before he went on it full time.  He needed it at night because people's oxygen levels will tend to drop while they are sleeping.