The terminology appears to be somewhat mixed up. xplusone<int> is not a specializaton, just an instantiation of the template.
Specialization is when you tell the compiler to use a separate implementation of a template when some or all of the template arguments match something. Template specialization is used in the type traits section of the post.
Specialization is when you tell the compiler to use a separate implementation of a template when some or all of the template arguments match something. Template specialization is used in the type traits section of the post.