Yet it's convenient that he allowed George, Charlotte and Louis a title, and never acted on slimming down the RF....until now. He didn't with George. Nor Charlotte's birth. Nor Louis' birth.
I've already posted this on this thread but, there was a reason they did it for William's children. Setting aside all personal issues with the various personalities, William's first born son would have been titled 'Prince' anyway under the LP which stated that 'the eldest son of the eldest son of the Prince of Wales' would be HRH Prince RoyalBaby.
The same didn't apply if they had a girl. Because of the revisions to the succession rules which meant a female baby would not be skipped in favour of her brothers, they could have ended up with a situation where William had one, or several, girls, and then a boy that outranked his sisters in terms of title but not in terms of succession. The Queen did it to maintain clarity around 'rank' in the family which otherwise would have been confusing. The simplest way to do that was to say 'all of Williams children' rather than 'all of the girls but not subsequent boys after the eldest' which just wouldn't make that much sense.
There was a clear reason for it when you look at the various laws involved. The same isn't there for Archie. Regardless, William's children are the children of the man that will be King. Harry's are not. They are members of an institution that is all about rank and status, and that makes William's children, frankly, more important when it comes to that status. It isn't about Charles being fair and treating the sons equally as it might be in a personal context, because in terms of laws around titles and succession, they aren't.