In the documentation regarding built-in privileges in section "Profiles reference", both "usage_on_schemas" and "usage_on_schema" appear. Only the first parameter is correct; the second one can be misleading and doesn't work.
You're right @tstepien0 !
The error is actually in the Profile all_on_schemas section.
The privilege __usage_on_schema__ must be __usage_on_schemas__ to be functional!
In the documentation regarding built-in privileges in section "Profiles reference", both "usage_on_schemas" and "usage_on_schema" appear. Only the first parameter is correct; the second one can be misleading and doesn't work.