Again, quoting the "exclusive" story from Matt Wilkinson in The Sun on September 15:
Several members pointed out that the claim that the King will issue letters patent to
confer prince and princess titles on his grandchildren does not seem to make any sense.
If one accepts the view that King George V's letters patent of 1917 remain in force until repealed by a new letters patent, then the 1917 letters patent automatically conferred prince and princess titles on Archie and Lilibet at the moment of their grandfather's accession, and no new letters patent are needed to confer those titles.
Even if one accepts the point of view that the Sovereign's will is all that is necessary, the King has no obvious reason to have overturned the existing letters patent by his Will, if they are already in accordance with his alleged wishes that all his male-line grandchildren be prince and princess.
However, after reading another article in the Sun a few days afterwards, as well as Durham's question earlier in the thread, I think there is some (arguable) logic to the claims about new letters patent. The September 19 article says:
His Majesty, has agreed to issue letters patent to confer Archie will receive the title of prince in the future, alongside his sister Lilibet who will receive the title of princess.
However, Meghan and Harry's baby boy will not be called His Royal Highness - thanks to his great-great-grandparent.
King George V introduced a rule in 1917 which means their baby would need special permission from the King to receive HRH status.
Only the eldest son of the Queen's first born, King Charles, is entitled to be a HRH - no younger sons or daughters.
[...]
Despite Royal protocol, in December 2012, before Prince William and Kate Middleton had their first born Prince George, the Queen used the Letters Patent so she could give all of their children an HRH title.
https://www.thesun.co.uk/news/8150244/baby-archie-royal-title/
This second article was not written by the same author as the original "exclusive", and it is unclear if it is credible or not.
But, putting the Sun's stories together, I think this is what the Sun is
claiming is going to happen: A statement is issued which makes the dubious claim that the 1917 rules only entitle children who met the criteria (child or male-line grandchild of a sovereign, or the eldest son of the eldest son of the Prince of Wales) at the time of their birth, and that others who were "only" great-grandchildren at the time of their birth (Charlotte and Louis, Archie and Lilibet) need fresh letters patent to receive royal titles, such as those issued for Charlotte and Louis in 2012. The statement continues and says that the King has decided to issue letters patent for Archie and Lilibet as well, but because they are not expected to become working royals, their letters patent will include only Prince and Princess but not HRH. (Again, this is
not my personal prediction. It is what I think the Sun is alleging will happen.)
If (and it is a big if) the Sun's prediction is accurate, it would be very questionable from the legal point of view (I don't see any evidence for the "only at birth" interpretation of the 1917 letters patent), but I suppose the advantage would be that Archie and Lilibet would ostensibly never have been stripped of anything, but rather had titles specially gifted to them by their grandfather which they would otherwise never have received.