It means that Jamie was having one bad day, the poster saw this and thought he is like it all the time. Maybe he is, maybe not.
I've seen this exact same behaviour wiuth a number of the famous golf pros when having to sign autographs and do press meetings etc.
They start off when young - can't do enough, sign a million autographs and answer questions, give up their time etc; it seems glamorous..
A few year's later, it all becomes harder, they get less tolerant and try to avoid the distractions and demands of the adoring public.
Not all are like this of course.
The public don't understand how demanding they can be, and people can be downright inconsiderate and rude. Just ask any shop assistant who has a few years under his/her belt...