If a client wishes to explicitly register an existing notification
by issuing a GET request, it MUST also additionally supply the URI
containing the conditional attributes that was conveyed to the server
during the registration.
I think you mean:
If a client wishes to explicitly cancel an existing registration by
issuing a GET request, then the request URI MUST specify the same
conditional attributes that were specified in the original registration
request to the server, with the same values (if any).
From https://mailarchive.ietf.org/arch/msg/core/mBfPbB892W95BnAHEq9wtv8aH9Y/
[Section 3.4]
The text says:
I think you mean: