Everyone has a futaba charger... and it is common practice to use centre pin positive... So as the Spektrum charger is useless in the UK it makes sense to modify the transmitter so it accepts the same charger as every other transmitter we use (And everyone else). It also means that it cant be damaged by plugging in a futaba charger or any other that uses centre pin positive.

The charging socket is seperate and on fly leads so is very simple to modify.