QED.
One size does not fit all (even within a generic type). The Final Director only has capacity for so much flexibility and now that 2.5nm is "expected", he has less room for error too.
In an ideal world, an advanced ATC support tool would provide accurate guidance for the different pairs in the sequence, taking into account their individual Vref on the day - but that day is still some years away. In the meantime, the priority should surely be to protect the system by creating slack. It is not the job of the individuals to make compromises on good practice in order to make the numbers fit.
.4
