Hello!
It is not a bug. The problem is that you try to use correspond to my original sugestion and not correspond to its implementation in jqGrid. You should define cmTemplate as the jqGrid parameter and not as the default setting $.jgrid.defaults.cmTemplate. Moreover you want use the setting not for all columns you can use template property of colModel instead.
For example you define
var myGeneralFormOption={ formoptions:{ elmprefix:' ' } }
and then use it in the column where you need it:
{name: "api", index:"api", search:false, hidden:true, template:myGeneralFormOption,