I can totally imagine they're using Tor for some undercover (foreign) operations or similar. I don't think the US Government with all its branches is known to practise exactly what it preaches.
The US government has different parts with different goals: https://www.washingtonpost.com/news/the-switch/wp/2013/10/05... (paywalled). IIRC, the NSA has interests in conducting surveillance, and the State Department has interests in allowing liberal foreign dissidents to defeat surveillance.