Is it somehow shocking that a probable cause standard doesn't apply to national security intercepts of cross-border communication? Customs doesn't need a warrant to search your bags at the border, either.
The key point of FISA is not to legalize spying on communications among foreign nationals or between foreign nationals and Americans. Such spying has been considered part of the Executive's national security authority for decades. The key point of FISA is to ensure that intercepts between Americans that are subject to Fourth Amendment protections are avoided by design and deleted when discovered.
Congress couldn't obligate the Executive to get an "Army Court" order before ordering a division to take a city. There's a little more sense to the obligation here, since they're just as responsible as any other branch of the government for protecting Americans' Constitutional rights. But these orders aren't meant to act as warrants: They're oversight tools.