The problem is, you really can't rely on any of the data we have so far as credible. The ship at least tested a broader range of sick and healthy than has been done outside the ship but it's still a thin sample and the people tested outside the ship have primarily been either moderately to severely ill and so that's a very biased sample.
IMO, the primary value of this article isn't the estimates built around the ship data, it's:
1. Pointing out the current data is crap, for the reasons I said earlier
2. Citing the fact that other known diseases with very low mortality rates as a whole, still have significant rates for the elderly with existing health problems — and we don't have any data which suggest yet that this is any different than those diseases in that regard.