But it's a "right" that can be taken away so is it really best viewed as an award or a privilege that can be revoked?
It's interesting that the LPs use the phrase "at all times hold & enjoy" because that suggests permanence but monarchs can undo the LP's of previous monarchs at will so these titles etc are not set in stone at all but subject to review &/or removal/abeyance.
Maybe George v did not understand this? Although I would imagine he did because his own LPs of 1917 deprived male line gt grandsons of British monarchs from being HH/prince - which up until that point had been their "right".
I think letters patent are as permanent as anything under the law. The British monarch uses them to appoint the great officers of state, the judiciary, the church leaders, key military leaders, royal household officials, key academics, and so on.
George V (and his advisors) certainly understood the purpose. He used them to change the name of the royal house, remove the German titles from his family members, and refocus the use of titles.
Just as his letters patent overwrote previous laws, new ones could overwrite his.
If Charles wanted, he could limit titles to William's line only, although it probably wouldn't be worth the media backlash when the Sussexes and their supporters responded. I imagine he'd much prefer Harry to announce that the kids aren't using their titles, just as Edward did.