Finally!
Great post. Thanks for highlighting that the Queen had already gone the extra mile for William's kids, and Harry and Meghan may have wondered why not for him too.
I believe that they thought the Letters Patent would be updated for their children too, as they were for C and L. It was a kind and thoughtful gesture to "equalise" all William's children and give them the same rank as George. I would have thought Harry in particular would have understood this because it is precisely the heir and spare nonsense that he suffered from as a kid.
But to be fair to them, to not only find out that this was not going to happen, but that the existing LP applying to their kids would actually be amended to "unprince" them must have rankled, and convinced Harry that his children were "lesser'!
As it is, they have played a tactical move. I have a feeling Charles wanted to issue LPs to remove the titles, but they have put him in a position where he can't do that, after Frogmore. At the same time, this is a very bullish action indicating they are very much part of the monarchy, in or out. And you can expect them to come to the Coronation😅