Sounds very much like cost cutting to me. However you may find out so much more on this brilliant site if you click the link below. Lots to read, makes sense and you can see just how little the medics know about this condition. Btw P.A is not the same as B12 deficiency, there are different causes for this, even down to it being an hereditary condition.
Good luck with your results but why didn't they fully establish it was PA in the beginning, that's why I think it's cost cutting as many patients are having their jabs withdrawn.... Or as in my OH's case refused treatment.
http://www.b12deficiency.info