I refer to The OpenCL Specification, version 1.2, document revision 19, dated 11/14/12.
Table 5.16 describes the queries possible with function clGetKernelWorkGroupInfo. The row describing CL_KERNEL_GLOBAL_WORK_SIZE contains the following statement:
"If device is not a custom device or kernel is not a built-in kernel, clGetKernelArgInfo returns the error CL_INVALID_VALUE."
Giving information on clGetKernelArgInfo seems out of place in this context.