This major doctrine, so idiosyncratic to the JWs, results from an eisegesis methodology which imposes a conceptual frame onto a text rather than discovering from the context what concepts are expressed therein. A little reflection can show how eisegesis is the usual approach taken by the WTS in interpreting Revelation.
Hmmm, sounds like an intellectual way of saying, "Rutherford made the sh#t up to account for the number of his flock exceeding 144,000 and imposed that on the text rather than reading the text in context."