It is the same story as the key performance indicators in employee assessment. People stop working to the wealth of the enterprise and instead focus on the growth of their indicators.
If this is possible, we've proved that the performance indicators do not indicate what you defined as "performance" but something different and thus should be dropped.
The point is that the algorithm isn't what people are currently trying to get past, they are trying to get past human hiring. When they switch to a strategy gaming the algorithms instead of the humans then the algorithms can become worse than nothing depending on how quickly the information race goes.