I think he has a warped idea of what the word work means. I would suggest he took the job under false pretenses and misled his employer. He claimed to be a cake decorator when in fact he was only able to decorate a limited number of cakes. He would have known that there would be an expectation to produce finished cakes for a number of occasions but also knew he would not be willing to decorate any of the seasonal items.
What is annoying is this person took the job away from someone else who would have been willing to work and who would have been able to have a good christmas themselves with a wage coming in.