Devops yaml string array not recognized when passed as part of complex object type parameter and coalesced with another object

Question

You can loop through and print the strings in an array passed as a parameter to an Azure Devops Yaml Pipeline Template. You can also loop through a string array passed as part of a complex object, or coalesced with another array - but not both.

Below I have 2 working examples and then the one that crashes.

Working example #1

azure-deploy.yml:

extends:
  template: azure-deploy-template.yml
  parameters:
    complexObject:
    - drink: 'water'
      foods:
      - 'apple'
      - 'banana'

azure-deploy-template.yml:

parameters:
- name: complexObject
  type: object

jobs:
- job: TestJob
  pool:
    vmImage: 'ubuntu-latest'

  steps:
  - ${{ each o in parameters.complexObject }}:
    - ${{ each f in o.foods }}:
      - script: echo '${{convertToJson(f)}}'
      - script: echo '${{f}}'

outputs:

"apple"
apple
"banana"
banana

Working example #2:

azure-deploy.yml:

extends:
  template: azure-deploy-template.yml
  parameters:
    animals: 
    - 'cat'
    - 'dog'
    complexObject:
    - drink: 'water'
    foods:
    - 'apple'
    - 'banana'

azure-deploy-template.yml

parameters:
- name: animals
  type: object
- name: complexObject
  type: object
- name: foods
  type: object

jobs:
- job: TestJob
  pool:
    vmImage: 'ubuntu-latest'

  steps:
  - ${{ each o in parameters.complexObject }}:
    - ${{ each f in coalesce(parameters.foods, parameters.animals) }}:
      - script: echo '${{convertToJson(f)}}'
      - script: echo '${{f}}'

outputs:

Same as #1

Problem case

azure-deploy.yml

extends:
  template: azure-deploy-template.yml
  parameters:
    animals: 
    - 'cat'
    - 'dog'
    complexObject:
    - drink: 'water'
      foods:
      - 'apple'
      - 'banana'

azure-deploy-template.yml

parameters:
- name: animals
  type: object
- name: complexObject
  type: object

jobs:
- job: TestJob
  pool:
    vmImage: 'ubuntu-latest'

  steps:
  - ${{ each o in parameters.complexObject }}:
    - ${{ each f in coalesce(o.foods, parameters.animals) }}:
      - script: echo '${{convertToJson(f)}}'
      - script: echo '${{f}}'

This fails with the error: Unable to convert from Object to String

If I remove the last line in azure-deploy-template.yml, just the json outputs. Output:

{
  "lit": "apple",
  "style": "",
  "line": "13",
  "col": "5",
  "type": "0"
}
{
  "lit": "banana",
  "style": "",
  "line": "13",
  "col": "5",
  "type": "0"
}

Why is the string array being interpreted as this strange complex object?