I know I'm late. Just happened to be here, having the same issue. I don't know how to make this work, but I can guess why yours act like that. That CSS is much like a visual hack rather than a solution. It only hides the handle. The functionality is still there and so it functions just like before when you have two slider handles. The difference is only that the handle is invisible because of the CSS. Depending on the visible handle, it may show a time span. With left handle, it will show time span when you slide to the left. With the right handle, it will show time span when you slide to the right. It will still show time span until you "snap" those two handles, which one of them is invisible.
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