This is what I think H&M are thinking.
We have stepped down as working royals. We no longer have any perks of being royals. We don't cost the taxpayers anything. We are free of the restrictions of the RF because we don't cost them anything, they don't do anything for us and we don't do anything for them. We should be free to do whatever we want now, and obviously that means earning a living. So, we should be free to use social media however we want partly because that's how we will earn a living, we should be free to go wherever we want, live wherever we want, say whatever we want, brief however we want, raise money however we want, use our voices, shine lights, use whatever PR, grift and you have no right to stop us and we don't owe you anything.
HOWEVER, of course I'm still the King's son and these are still the King's grandchildren, and none of us asked for this and none of us can do anything about this. None of this is our fault. Therefore, it's not up to me to pay for security - it's up the King and the apparatus of the state. Moreover, we shouldn't have to accept any restrictions on our lifestyles or choices just because it would be cheaper for you - it's not our fault, after all, that we are born to our parents, why should we pay for any of this. And, obviously, it goes without saying that the damage to the United Kingdom and the royal family and the world as a whole, of anything being seen to happen to us because the country couldn't keep us safe, would be immense so actually it's in your own interests to protect us whatever we decide to do and however we choose to live. This is your duty to us.
(The obvious answer is to stop him being the King's son (ie a Prince) and the King's grandchildren (Prince/Princess) - although of course they will always be Charles Mountbatten-Windsor's child and grandchildren. And this is where I think this is going to end up but we're not quite there yet - I also don't believe Harry can imagine this ever happening.)
Harry was raised to revere his grandmother as Queen/HoS. Meghan wasn't. Harry thrived in the structure of the Army, Meghan lol-ed at a conference that she's such a fraud for getting away with pretending to be a union actress to get gigs when she wasn't. She lives by faking it until she makes is (although so far there's been a lot of faking being a Duchess and never quite making it). There's only one person who would have dared to say "collaborate with the Queen", "nobody owns the word 'Royal'" and I'm going to wager it's the one who refers to the HoS ALWAYS as "your dad" and the PoW ALWAYS as "your brother" and the late Queen ALWAYS as "his grandmother". It's going to be the one who uses HRH when she's been told not to, and the one who will stop at nothing to get what she wants including dropping family, friends, husbands - anyone - who stands in her way.