Are all these values equal on different stages? Is it always so? What about getUniqueValue()?

Sys ID values on insert of new record.md

var kb = new GlideRecord("kb_submission");
var sys_id_before_init = kb.sys_id;
// undefined
var sys_id_before_init = kb.getUniqueValue();
// null

kb.initialize();

var sys_id_after_initialize = kb.sys_id;
// ""
var sys_id_after_initialize = kb.getUniqueValue();
// null

var sys_id_insert = kb.insert();
// guid1

var sys_id_after_insert = kb.sys_id;
// guid1
var sys_id_after_insert = kb.getUniqueValue();
// guid1