Sort of true, but not really.
If I recall correctly, in addition to commercial support, MoodleRooms also contributed back to the code base. I don't know the percentage of improvements that came from them, or from NetSpot, but I'd bet they were solid components if someone was willing to pay to have them written. And there's all the improvements related to running Moodle as an enterprise app, as opposed to on an old 486 in the back closet, which is often how many installations start out.
If Blackboard's plan is to harm Moodle, they could do worse than taking out some of the key development partners - over time, simply stop contributing. It's slow, but they can't kill the product all at once anyway. So they could collect revenue for a while, and at the same time take development resources away from the community. Eventually the customers decide to move, because the product no longer supports (shiny new thing), and look! they already have a relationship with Blackboard!