I do not know how many journalists were killed in most conflicts. I do know more than 242 were killed during world war 2, so on its face the claim seems false that it is the deadliest war for journalists in the history of the universe.
The only way their claim can possibly make sense is if they are using different definitions between wars. I'm assuming that to give them the benefit of the doubt. The only alternative explanation i can see is they are straight up lying.
I don't know enough to verify related claims, like deadliest for journalists post world war 2. However given the source seems to be blatently incorrect, i'm not really inclined to believe them on related claims.
I said that the nature of journalism has changed since ww2, because there’s a lot more citizen-journalism - which probably means there are more journalists around to be killed today than during most conflicts in history. So it doesn’t actually surprise me that the highest number would be from a conflict post-2010.
So unless you have some clear evidence that the definition of journalist is different in other conflicts, you’re just making excuses.