Hard forks happen. As a financial institution who wants people to trust their money to them, it's common sense that they spell out what they would do in such a case. It's part of their fiduciary duty to do so.
Imagine they didn't say it, and there was a(nother) hard fork. How do they decide what to do? They would open themselves to lawsuits and what not. Now that's out of the way (in part - I'm sure someone would find ways to sue them anyway).
The play is the confiscation of a large enough amount of BTC.