They wouldn't know, but I suspect they nip it in the bud when asked by donors. If a donor asks if they should donate through the foundation or direct to the HWC, the foundation tells them they want it all.
They wouldn't be doing their job if they didn't. Now, that isn't to say they need to be dicks about it.
So, just to make it clear to everyone, you are free to donate to the HWC and the foundation doesn't need to know about it, nor can they do anything about it.