I asked someone from TN Native plant society. Here's his rather complete answer. Does anyone agree / disagree? I'm thinking he's nailed it otherwise.
"Did a little more study on your plant and I am pretty convinced it is Smilax eccirhata. I believe all of your plants are females based on the flower in the middle photo and some that were opened in the third shot. That means they are probably all clones of the same plant that has just made a clump by vegetative propagation. This would explain why you only see one flower cluster because I believe female plants only have one cluster (or maybe two at most) and the males have more clusters and there are 5-pointed "stars" of stamens vs. the 3-pointed "stars" formed by the stigmas of the females. And if you don't have any male plants, you wouldn't get pollination and therefore never see fruit. Also, these thornless herbaceous Smilaxes have thinner, "rougher" looking leaves as compared to say catbrier, especially when they are first coming up. In any event, you've got a nice clump of very attractive plants!"