only/except tags unexpected behavior with extends

It's somewhat surprising that when using extends, only: - tags and except: - tags will be merged, and the result is that a tag job will be lost:

build:
  variables:
    BUILD_TYPE: "Build only"
  script:
    - echo $BUILD_TYPE
  except:
    - tags

build and push:
  extends: build
  variables:
    BUILD_TYPE: "Build and push"
  only:
    - tags

Workaround:

build:
  variables:
    BUILD_TYPE: "Build only"
  script:
    - echo $BUILD_TYPE
  except:
    - tags

build and push:
  extends: build
  variables:
    BUILD_TYPE: "Build and push"
  only:
    - tags
  except:    # override       <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<