Gitlab CI variable expansion in needs

needs: already expands variables if it is a crossproject/crosspipeline reference
(according to https://docs.gitlab.com/ee/ci/yaml/#needs)

Is it possible to get this variable expansion as well if only job: is used:

build proj1:
  ...

.test-base:
  needs:
    - job: build $Project

test:
  extends: .test-base
  variables:
    Project: proj1
  ...

This currently does not work for me, it fails with "yaml error"
runner version is 13.2.1 gitlab-ee omnibus version is 13.4.0-ee (e70802d3)