Most sign languages (which emerge naturally just like spoken languages, some even think that they might have been there before) have simple, atomic signs for concepts/things. There are combinations of course, like pointing to your earlobe to add "female" to the sign before. So the specialty is that this language has no such combinations at all?
There are also parts of sign languages which aren't categorized clearly, especially when explaining visual/spatial circumstances. When signing "I bought a table, it's wooden and has a fine white line engraved along the edge." you probably won't use signs for "fine", "line", "along" or "edge". You would just describe it visually. There is probably not even a sign for "edge" which applies to this context. Again, I'm not a linguistic expert, but I think that some of these characteristics might be hard to squeeze in "It's a word or not".