I can think up 3 possibilities
(1) He needded to apply for a visa
(2) His visa is till valid ( i doubt it because he entered USA on first entry in the beginning of 1990
and I think F-1 visa entry period is only 6 month)
(3) Beneficciary of Chinese Student Protection Act
(advanced paroled).
If (3) is the case, he really said something
stupid.