Regarding this issue, I think the iNat community has created a problem largely in search of an example (honestly, the risk would be quite low of individuals actively harvesting coordinates for rare species, unless we're talking species like white rhinos)
Given that the disadvantages this mechanism presents largely outweighs the risk, I think it would make sense to come up with some solutions, no?
Why can't projects "read" true coordinates while displaying obscured coordinates? This shouldn't be technically difficult to code, and the result should ensure projects include observations of rare species within their boundaries, while still obscuring those observations from the general public. Granted there may still be a risk of iNat "poachers" creating tiny projects to ascertain the locations of rare species, but this seems like a ridiculously small risk, and it could easily be monitored by tracking users who create projects with areas smaller than 500m2 (for example).
Another solution is simply to provide trusted users with access to the coordinates. Surely this solution wouldn't be terribly difficult to implement?