Yeah, we have definitely not seen Shallan's shardblade, and Honourblades have been confirmed. I don't really know what business Cultivation would have for making shardblades. All I know is that we've seen three: 1) Honorblades, wielded by the Heralds; 2) your average, run of the mill shardblades, which Syl seems to hate, and the only other thing we've really seen her hating is Odium, so I'm connecting them for now, as tenuous as that connection may be; and 3) Szeth's smaller shardblade which would be taken back to Shinovar, a place many theories connect to Cultivation. As I have stated, I don't currently have a lot of ground to stand on; this is mostly just speculation. However, I feel rather confident in my interpretation of the data I currently have at my disposal. Also, I just discovered I'm not the first to suggest the Odium connection.