Yaml模板表达式返回false

在下面的示例中，Azure DevOps模板表达式始终返回“False”，即使参数为真。为什么？

主yml：

trigger: none
pool:
  name: Azure Pipelines
  vmImage: windows-latest

variables:
  - name: myVar
    value: true

steps:
- checkout: none
- powershell: |
      Write-Host "myVar = $(myVar)"
- template: TestJppTemplate.yml
  parameters:
    myParam: $(myVar)
- powershell: |
      Write-Host "myVar = $(myVar)"

测试JppTemplate.yml：

parameters:
  - name: myParam
    type: string

steps:
- powershell: |
    Write-Host "myParam: ${{parameters.myParam}}" # Display true
    Write-Host "expression1: ${{eq(parameters.myParam, 'True')}}" # Display False
    Write-Host "expression2: ${{eq(parameters.myParam, 'true')}}" # Display False
    Write-Host "expression3: ${{eq(lower(parameters.myParam), 'true')}}" # Display False
    Write-Host "expression4: ${{eq(parameters.myParam, true)}}" # Display False
    Write-Host "expression5: ${{eq(parameters.myParam, True)}}" # Display False