I think this is not terribly inaccurate - perhaps stated with a little more confidence than would be conveyed in internal communications. Also, the "largely secular" part could be a bit of a fudge. I've listened to a couple of Egypt experts in interviews over the past few weeks, and the consensus seems to be that the make up of the MB is somewhat unknown. My understanding is that there is believed to be at least a significant secular minority and a significant radical minority, but much more than that is hard to tell, and where exactly the centers of power are within that spectrum is harder still to determine.
This breadth of ideology, from the seemigly secular to the seemingly radical, is illustrated pretty well, for instance, in the following two recent stories:
1.
http://www.tehrantimes.com/index_View.asp?code=235393
2. http://www.eurasiareview.com/world-news/africa/muslim-brotherhood-rejects-khamenei-calls-for-iran-style-islamic-state-05022011/