But the lich doesn't care if they know it.
Redcloak is not the boss here. Apparently he has convinced Xykon to kick back awhile until he can do some research, but the plan is to leave the city and soon. Redcloak is not going to get the time off to chase down the last of the paladins.
Now one piece of information he might want is that the humans have a lot of ships, and the lich will want to take his army with him. So that information could have consequences.
And Xykon's reaction is likely to be "Who?", followed by a yawn. He just does not consider the OOTS a threat, with pretty good reason.