I believe this is unlikely to be changed, since the default behavior needs to apply to both a single-value selection but also to selecting multiple values. Without a confirmation box, the latter becomes impossible. Qlik has largely resisted this sort of toggle in Sense thus far, so I would be somewhat surprised if this sort of thing was added.
Do note that some extensions, such as Vizlib Table, do have the option to switch to "Single select mode" where you can't select multiple values and as a result, confirmation is not required, so if this is a critical issue you could look into using an existing extension or possibly creating your own.
