I have generated Smart Previws, but the interface only shows "original". Restart LR and now I see "Original + Smart" under the histogram. Not sure if that is just a display issue or if Smart Previews are really not being linked.
I'm having the same problem. Lightroom says the image has a smart preview under the Histogram but their is no icon in the image preview in Grid view. Did Lightroom do away with the badge in 5.2? Yes, I am working with RC 5.2