What I have heard, the reason of the Unknown is because the tree has multi language support (FTB) but the owner has only filled in one of them and missed the setting to automatically copy info from one language to the other if one is left empty.
The problem is that it probably looks OK for the tree owner.
The reason for this may indeed be that the tree that you were matched to contains two languages, however not all information is entered in both languages.
What I would suggest you to do, is contact the site manager of the other site, and request him to fill in the data in both language. You can do so through the Smart Match page directly.
