Yes, this bothered be as well - the department of government efficiency is, as with all government agencies, is working for the public good in the public interest. This means everything must default to being open, unless there is a good reason not to be (military, CIA etc).

I don't trust Elon, and don't see why DOGE should (or could) be secret - unless it's a cover to acquire more power, which seems to be his true objective. (recently, at least)

Signal is widely used among high-ranking and/or appointed officials in the bureaucracy. From what I have observed, this is true on both sides of the aisle.