Unable to use `env` variable in a container name

Describe the bug
I'm trying to use env variable inside container name and I'm getting Startup Failures.

To Reproduce
Use env variable in a container name specifier. Example:

name: env in container name

on:
  push:

env:
  IMAGE: ubuntu:18.04

jobs:
  build:
    runs-on: ubuntu-latest
    container: ${{ env.IMAGE }}
    steps:
      - name: env
        run: echo ${{ env.IMAGE }}

Expected behavior
Workflow should start with container from env.IMAGE
env context should be available: https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability

Runner Version and Platform

Can't tell, it doesn't start.

OS: Linux

What's not working?

Workflow doesn't start.

Status Startup failure

Invalid workflow file: .github/workflows/env_container_name.yaml#L12
The workflow is not valid. .github/workflows/env_container_name.yaml (Line: 12, Col: 16): Unrecognized named-value: 'env'. Located at position 1 within expression: env.IMAGE

Found this and it's missing env: https://github.com/actions/runner/blob/ca7be16dd3b90be39775987995ce4c9dd8bdf7d8/src/Sdk/DTPipelines/workflow-v1.0.json#L367-L373

Job Log Output

n/a

Runner and Worker's Diagnostic Logs

n/a

Start with the workflow example in .github/workflows/env_container_name.yaml at line 12 and inspect the referenced workflow-v1.0.json schema around its container name definition. Confirm how context availability is represented for container expressions, then verify that the workflow accepts env.IMAGE and starts with the requested container.