Holding their reserves in something other than cash is the way they can make money. The community will consider it betrayal because it essentially relies on the existing system they loath. But other than that, there isn’t too much wrong with it.
That may also point at a reason why they would want to keep this private, which otherwise seems suspicious.
That doesn’t mean people won’t lose all or some of their money with them. Some of these holdings may not be as liquid as needed in a full-on bank run, and they, like all stablecoins, suffer from the mismatch of having no upside by definition but some downside risk.