You can believe it, but it is simply not true. It was originally an exclusive deal until fans got upset and congress got involved. Only after that, they opened the deal to anyone who matches DirectTV's offer which seems like a good offer but in reality unmatchable by other providers. I actually think it was a smart business move even though I hate it as a fan shifting the blame on the other providers while knowing that it will eventually be exclusive because no one can match it. If anyone complains they can say everyone had a chance. Look at the details on the latest InDemand offer... MLB and DirectTV want it as an exclusive.
I don't believe in any way that the idea was to have this as an exclusive. The way I see it - MLB originally laid out parameters for the various providers - such as carriage of the MLB channel on their most basic tier, etc.