I wouldn't say that they "prefer supporting" it, it's more that a closed project is ... ignorable? It doesn't really bother them, because the only things that will happen are on a scale from "never hear about it again" to "get patches from that company". Compare that to someone making the code GPL, which means that they can see, but not use, everything the other part does to it: When you also know that making it GPL is completely unnecessary, it almost seems like taunting them. Besides, they're probably less likely to get patches from a GPLed fork, since the people involved in that will probably think "oh, it's already open".
So, yeh ... from a BSD point of view, a closed program using some of their code is probably preferable to a GPL project making it GPL-licensed. (Again, this is different from a GPL-ed project using it under the original BSD license, which is a good thing.)