You bring up some good points here since we don't know who and if any riders really spoke with the USADA.El Paso I agree with you 100% about USADA but they have also selected only those who have said he cheated and willing to testify but they have interviewed and spoken to a whole lot more than the 10 they have on board but these riders said either they will not testify or stated he did not cheat and these riders are of no help to USADA cause.
It would do USADA more service and credit if they said how many were approached and how many said no he did not cheat, how many are no comment as well as the 10 we know of.
Its a lot like only counting the votes in an election that support your cause!!
I'm thinking that this may have been the prime problem that the federal investigators ran into, thus causing them to close their case.
I observed a faslness in Travis Tygart during the USADA vs Floyd Landis case and I wouldn't put it past him to continue doing so.