Do I need a custom 128-bit UUID if I delete one or more Characteristic from an Adopted Service

[Renix]

Do I need a custom 128-bit UUID if I delete one or more Characteristic from an Adopted Service I do not modify the remaining Characteristics

For instance: Sniffing with Master Control Panel \nRF5_SDK_13.0.0_04a0bfd\examples\ble_peripheral\ble_app_hrs\pca10040\s132\

One of the services used is Generic Access, but only three (3) of the 5 Characteristics are used. But then a Characteristic Central Address Resolution UUID 0x2AA6 shows up under the Service

Should not this then be a Custom Service, with a 128 bit UUID? Device Name UUID 0x2A00 Appearance UUID 0x2A01 Peripheral Preferred Connection Parameters UUID 0x2A04 Central Address Resolution UUID 0x2AA6

[endnode]

If these are standard Services and Characteristics defined by BT SIG Core specifications (and amendments) then it must use assigned 16-bit UUID, otherwise GATT Clients cannot understand it. Why you would define custom UUID so only your app would understand the hierarchy under its tree?

[endnode]

Central Address Resolution Characteristic must be only one on the GATT Server and it must be under GAP Service. As I don't see this specifically used anywhere in SDK I assume that Security manager layer inside BLE stack (Soft Device) automatically exposes this Characteristic if you enable privacy with address resolution through other SVN (Soft Device API) function calls. So no need to manage it yourself, it is OK that you see it as GATT Client if this is enabled on GATT Server and it's a pitty if you want to support address resolution but hide this characteristic because it's mandated by BT SIG Core specification and thus Soft Device handles it automatically. But this is just my assumption. Is it in-line with your observation?