This explanation doesn't sit well with me, and i sincerely hope it is not anywhere near the truth...
This is their game now. If they want to implement a new gameplay feature, or refine a feature they already have, they shouldn't have to care if someone's already made a mod for it.
Besides, what do you think inspired Hoppers (chutes) and Enderchests? (it even shares the same name)
Oh, and also horses I'm pretty sure was even helped along by the creator of Mo Creatures, the new biomes I recall hearing something about BoP being involved... (Don't quote me on that)