理解有誤，sorry

又重新看了一下212e，http://www.visalaw.com/IMG/212e.pdf
的確是要求physically present in the country of his nationality or his last residence for an aggregate of at least two years following departure from the United States.
因為想如果是出公差去別的國家應該也算回國服務期，看來還是不算。