I didn't find that surprising at all. That is the way the contract business works.
If a company is contracted to provide a specific set of functionality, their focus is to provide that specific set of functionality. If their requirements are met, then they have fulfilled their contract. It would odd for them to worry about integration (beyond what is part of their contract). The company tasked with, and paid for, doing integration tests is responsible for doing the integration tests.
That is normal in the software business.
(I just re-read my response and realized how odd it is that I give more blame to the Obama administration than Baldimo does, but I stand by my opinion).