There's plenty of reports of members of the RF - including the late queen and more recently Charles, so when head of state - being spotted (and not always recognised) out and about in public. Security is discreet and low key.
Also plenty of members of the RF don't have police protection unless on a formal royal visit/occasion. Only Charles, Camilla, William and Kate (and presumably the Wales children).
Obviously intelligence is shared as necessary with whatever private (unarmed) security they have, as they would with Harry's team, and if there is a specific risk/threat then security can be stepped up (as happened with e.g Salman Rushdie).
So there's no reason Harry can't wander round wherever he wants, with whatever private security he feels necessary.
Which is exactly what RAVEC is saying - give us 28 days notice, we'll take an up to date look at the risks and provide the security needed in light of those risks and his plans (where he's staying, what he's planning to do, the situation specific risks as well as the more general risks).
That doesn't automatically mean 24/7 armed Met protection, which Harry claims is necessary and to which he is entitled due to his 'status' and 'public service' - his words.