Self hosted windows runner executes yaml anchors in bash?

Given the following pipeline definition:

definitions:
  common-items: #https://stackoverflow.com/a/79179771
    - initialize: &initialize |
        Import-Module ".\.bitbucket\Virto_Functions.psm1"
        .\.bitbucket\initialize_step.ps1
pipelines:
  pull-requests:
    '**':
      - step:
          name: "Build & test"
          script:
           - $env:DISABLE_EAZFUSCATOR="true"
           - *initialize

My build then fails with the message

Any thoughts? It appears that it's executing this using bash and not powershell..

I have my entire pipeline working just fine using the documented YAML anchor functionality, but I stumbled upon this "hidden" feature on StackOverflow

I really want to have a way to re-use sets of scripts, instead of having to duplicate entire steps simply to leave out a few script lines