Thanks to some kind comments to my last blog post on the new developments at Ancestry.com, I have even more information about the lines. Please take time to read the comments to my post entitled, "Amazing, really cool developments from Ancestry.com" to see the complete information.
It appears that this development has been under construction for some time on a collection by collection basis. So whether or not you see it, depends entirely on whether or not you look at a collection where the effect has been implemented. It was apparently one of the features discussed at RootsTech 2013. There were quite a few things going on in my head at RootsTech 2013 and so it is not surprising that I didn't focus on this one detail.
The change caught my eye as something obviously useful and elegantly implemented. Thanks again to Ancestry.com.