As described in spec (1.8.1) individual fields (record, enum and fixed)
can also have its own namespace effectively overriding the enclosing
namespace.
In record, enum and fixed definitions, the fullname is determined in one of the following ways:
A name and namespace are both specified. For example, one might use "name": "X", "namespace": "org.foo" to indicate the fullname org.foo.X.
...
As described in spec (1.8.1) individual fields (record, enum and fixed) can also have its own namespace effectively overriding the enclosing namespace.