It would, but each nation deals with matters relating to its citizens in its own way.
And the other possibility is that the person of people involved may have been dual nationals (compare the Spanish authorities' statement giving the number of those with apparently Spanish names, which gave some idea of scale of their casualties but did not confirm specifically).
Or the apparently British person might be resident somewhere other than Britain. Or NOK could not be readily located. I could come up with quite a few other possibilities, but I think those are the main ones.