Having skimmed the judgement, it seems there's a whole apparatus with more than half a dozen key people and many minions required to ensure security for the cohort of people who require whatever degree of (armed or not) security in England, Wales and Scotland. I've also understood why Diana felt that keeping security meant she was being spied on: everything is coordinated through the monarch's private secretary (for cause). If you want security in those three nations, you have to tell the royal household who will cascade to the various people, who all report back to the royal household etc etc. Nothing moves very quickly, and the 28 day notice period seems very reasonable. Emails, phonecalls, meetings, documents back and forth. Personally I think the whole thing could probably be massively streamlined, but I'm not used to the public sector. I gather the civil service is as much about the nation providing employment as to the administration of government...
As for Harry, it's clear from the judgement that he was raised and was and still is accustomed to people doing things for his benefit and ease. From being addressed as "your royal highness" as a young boy, to asking for things and them happening, to people making decisions on your behalf - it all just magically appeared, without him ever having to think or do or pay for it. He has nothing to say about public funds being scarce. It's just "I want, I want, I want". On the other hand, I can see how he might have felt infantilised all his life: he's had decisions made for him all his life, either for his benefit or that of the monarchy as a whole.
The whole thing just reads as a very slow, very clunky machine in which various individuals are mandarins or pawns, moved about and manipulated for the better good of the country in return for a life of privilege and comfort. Harry wants the privilege and comfort, without any of the downsides. And it makes me think that Kate is as successful as she is because she chose this trade off, and had her eyes wide open. Meghan, not so much (and truthfully, I can see how she might have been frustrated by it all!).