Dev console buildconfig got [the server does not allow this method on the requested resource] error when not setting metadate.namespace

Test case is shown in below 

Using below to create a Buildconfig in GUI page of 
openshift console -> Developer -> Builds -> Create BuildConfig -> yaml view


  
~~~
apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  name: mywebsite
  labels:
    name: mywebsite
spec:
  triggers:
  - type: ImageChange
    imageChange: {}
  - type: ConfigChange
  source:
    type: Git
    git:
      uri: https://github.com/monodot/container-up
    contextDir: httpd-hello-world
  strategy:
    type: Docker
    dockerStrategy:
      dockerfilePath: Dockerfile
      from:
        kind: ImageStreamTag
        name: httpd:latest 
        namespace: testbuild
  output:
    to:
      kind: ImageStreamTag
      name: mywebsite:latest 
~~~

Get  [the server does not allow this method on the requested resource] error 

we can find even not setting metadata.namespace in CLI mode or by contact from the customer that in 4.11 GUI console will not trigger this error, Does that mean the code changed in 4.13 ?