This is just BAD practice. We should by default NOT do this and only very specifically do it if we have real alternative styles.
We currently apply the same style for focus as for hover, which in my opinion is simply not suited for the focus state. The only difference in this hover+focus style from the 'plain' style is a slightly darker green bottom line. I suggest taking a good look at github for instance, where they use a small dotted line, or they show the tooltip of the control for instance (the hover action).
As put eloquently here: "Stop messing with the default focus outline"