Kooljack, if this is the paper to which you refer:
https://fenix.tecnico.ulisboa.pt/dow...651/resumo.pdf
There is a diagram that appears to show multi-path propagation, is convergency zones. If that be the case it is possible that both ships indeed detected the same signal source.
Edit:
Lonewolf below: I wouldn't disagree with that and I am not advocating that it is definitely a CZ detection just that it is just possibly conceivable and should not be discounted.