QE II increased them for a different reason, to do with absolute primogeniture.
Sorry that makes no sense - there is no link between the two.
If you change the line of succession from first born male, to first born there is no reason why you also need to change things so that later born children become princes/princesses.
Let's, for the sake of argument compare the current situation to one where Charlotte was the first born and George the second born, but using the George V rules on who is titled prince/princess.
Succession based on first born male:
Actual: Prince George; Charlotte; Louis
Hypothetical with first born girl: Charlotte; Prince George; Louis
Succession based on first born:
Actual: Prince George; Charlotte; Louis
Hypothetical with first born girl: Princess Charlotte; George; Louis
There was absolutely no need to additionally decide to increase the number of princes/princesses from one to three.