I agree,it does seem too far.It looks as if James,the son of this James Myatt,is also described as "post boy" in 1861,having been "errand boy" in 1851.
However,the James Myatt you refer to is a railway employee up to and including at least the 1881 census(his initial employment record,Rugeley,1848,is on Anc****).
Regards
Roger