I might once have agreed with you.
But short term wins are that the Sussexes came over, all of them, and were received by grandad, privately.
They didn't get full-on security, they weren't papped, and were and I hope will remain safe and unharmed. That old chestnut has been exploded - H can't credibly bleat about security again
They didn't get BP or pics with The King, they got to meet dad/ grandad at the private, rented family home.
They didn't get the cavalcade or the public appearances.
The "KC3 is cruel and uncaring" trope is exploded. (Now go and see Thomas has already been put out there.)
The Sugars will have their few brain cells spinning and the more thoughtful ones will feel properly betrayed.
ThecSussexes has been humiliated. By kindness.
Long term, who knows what the BP plan is. I do believe that BP have a long-term plan - chess-like, thinking many moves ahead and considering many different scenarios.
ETA - I'm inclined to trust my King and his advisors at this point.