My point is that it doesn't require a trusted third party. Yes they seem horrible naive (academics usually are). A privacy "coin" where the govt has the backdoor key has essentially no utility. Bitcoin's pseudo-anonymous capabilities are more that sufficient for "casual anonymity" (not wanting your wife to know where you spend your money). Anyone interested in something stronger isn't going to be ok with backdoors.
You guys need to read between the lines. The authors are in the awkward position of explaining a way to make Bitcoin anonymous. They need a way to say, "see this could be set up so that the government could audit it" because this provides the "moral cover" to prepare the research in the first place.
But if you read between the lines, they've released the method for making this without such a backdoor, and that's all that matters.