I am not sure I got Your point…
Once You select flaps 1 in approach you will get S speed displayed, computed by the FAC based on aerodynamic or FMGC data. This depends on MSNs as “newer” ones (and NEOs) will display FMGC speeds based on weight data for consistency purposes, so you don’t have different characteristic speeds between the PFD and the MCDU values.
If you get slats locked the S speed will not change, hence pull the speed in order to avoid decelerating to a speed not suitable for that configuration.