It is working correctly, it's just that the visualization in the graph can be deceiving. Eg, if you have a transition between your keys that is slow then fast, then when you flip over the keys by scaling a selection box in the dopesheet, the transition between the keys is also flipped and becomes fast then slow.

In v4 the graph shows the curves where the X axis is time and the Y axis is the value, so it is more clear what is happening.