Hi there @clandestine!
On 1/30/23 the option to allow custom non-namespaced claims will no longer be available - That is, custom non-namespaced claims will be allowed in all tenants. The new restrictions along with tenants that have rules/actions adding non-namespaced custom claims that currently aren’t added to tokens (haven’t toggled off the setting) will introduce breaking changes when all tenants are moved over to the new behavior. This is the main concern and reason for deprecation language.
On 7/28/2022 the toggle to enforce that custom claims must be namespaced was introduced, and thus the ability to allow custom non-namespaced claims as well. By default, I believe this is toggled “on” for all tenants.
This claim will continue to be allowed - I agree that the messaging is a bit confusing here.
Overall, it’s easiest to think about this as toggled “on” as legacy no custom namespace behavior, and toggled “off” as the new behavior which will be enforced by default come 1/30/2023.
Great questions and I hope this helps to clarify!