Exactly. In a "roving wiretap" on a U.S. person that person is the target of the action. The Bush admin has repeatedly made it clear that whenever a specific U.S. person becomes an intelligence target they go the FISA route. The terrorist surveillance program does not target U.S. persons, it targets the overseas communication in manner standard for monitoring enemy signals intelligence.
It's not plausible that a U.S. Senator cannot comprehend this. Apparently they can, however, pretend not to do so for political purposes.
Seems that the reason why they insist on not understanding is because that way they are able to say that Bush is lying. It is why they showed that portion on the tape outside the hearing. That along with gonzales saying that he would advise congress asap if the President was involved in anything illegal. Showing of that tape was to help the 'people' understand that both Bush and Gonzales are liars. I wonder who it was who advised that the tape could NOT be shown.