There is a reason most banks exclude government receivables from line of credit borrowing bases. It is a legitimate market, but it is hiding in red tape and not plain sight.
That's not true at all and simply more hearsay and rumor. Banks see government receivables as reliably as if you invested in treasury bonds with cash assets. It's the only customer in the world that is 100% guaranteed to pay, on time, as long as you perform to standard. You're speaking to the wrong people if someone told you that. I'm speaking, however, from experience.