"This is probably out of fear on the part of the government that "N" = "n terms in office", where possibly n > 2; as in "liánrèn n jiè 连任n届" ("n successive terms in office"), which would be forbidden anyway because of the liánrèn 连任 ("continue in office") part."
I don't know any Mandarin or Cantonese, but this seems like a very strange explanation to me. Are there any native speakers with more insight on this?