It was, in respect of the Cambridge DC. The LPs that meant all the DC of the grandchild of the monarch in direct line (ie William) would be Prince/ss were issued in 2012 - George wasn't born until July 2013
It was done because the old LPs would have meant that if the first two DC had been born the other way round, there would have been the nonsense of the eldest, and next heir in the direct line being Lady Charlotte, whilst her little brother could have been HRH Prince George (though I would have hoped they'd have done a Wessex and not used it) followed by Lord Louis.
They still need a tidy up about male and female lines though, because it's royal styles only for DGC in the male line, and if George hypothetically has a daughter first, her DC would be untitled (unless the father were titled and they got something from him) whereas her hypothetical little brother's DC could be HRH Prince/ss. But the birth order of the little Wales means this can probably be parked for a decade or more!