ANA award availability is an indicator of what is available, but it is ANA's inventory. Not all the Star Alliance programs will have the same inventory depending on the airline you are trying to fly. I frequently find availability for a United flight award on the ANA site that is not available as a UA award. United allocates different programs a set number of seats and UA can already have used up their space allocation while ANA still has seats. ANA will show availability, but UA won't have any availability for Mileage Plus members.

This is how it has been with UA. It has happened several times when I have used ANA to search for availability using UA miles. Perhaps ANA has Austrian seats, but BD does not have any seats for awards left.