Are you sure for this translation ?

Hello, Kevin,
 
Thank you for reaching out to us.
 
Our team has not managed to reproduce the issue: when sorting is applied, the opposite sorting option is proposed on hover.
Please see the following JSFiddle example for illustration: https://jsfiddle.net/flexmonster/Lq9ekuct/
 
We would like to explain that by default values are unsorted, please see: https://jsfiddle.net/flexmonster/bvxLpsrq/
In such a case, it is possible for the values to end up being displayed in descending order, even though in reality no sorting is applied.
If this is not the case, could you please modify the following JSFiddle so the issue is reproducible: https://jsfiddle.net/flexmonster/Lq9ekuct/ ?
This will greatly help us to understand the situation better.
 
In addition, please kindly consider that is possible to specify the sorting in the slice configuration, for example:

slice: {
  rows: [...],
  columns: [...],
  measures: [
    {uniqueName: "Value"}
  ],
  sorting: {
    column: {
       type: "desc",
       tuple: [
         "color.[green]"
       ],
       measure: {
         uniqueName: "Value",
         aggregation: "sum"
       }
    }
  }
}

This way by default the values will be sorted in descending order and, hence, on hover, the tooltip will display Click to sort Asc.
 
Please let us know if this helps. 
Looking forward to your reply.
 
Kind regards,
Vera