AppPackageId token does not get resolved within the Site Scipts

Note: Sorry if it is more related to PnP Core. I can re-create this issue there, if that's the case.

AppPackageId does not get resolved when using Apply-PnPProvisioningTemplate

Install an App with app customizers that is not tenant-wide deployable. Let's call the app SPFxInstall

Create siteScript.json with the following contents:

{
"$schema": "schema.json",
"actions": [
    {
        "verb": "installSolution",
        "id": "{AppPackageId:SPFxInstall}"
    }
],
"version": 1
}

Create PnP_TenantDesign.xml with this content:

<?xml version="1.0"?>
<pnp:Provisioning xmlns:pnp="http://schemas.dev.office.com/PnP/2019/03/ProvisioningSchema">
<pnp:Preferences Generator="OfficeDevPnP.Core, Version=3.11.1907.0, Culture=neutral, PublicKeyToken=5e633289e95c321a" />
<pnp:Tenant>
<pnp:SiteDesigns>
  <pnp:SiteDesign Title="SPFx install Design" Description="Test design" WebTemplate="CommunicationSite" PreviewImageAltText="SPFx install Design">
    <pnp:SiteScripts>
      <pnp:SiteScriptRef ID="{SiteScriptID:SPFx Install Script}" />
    </pnp:SiteScripts>
  </pnp:SiteDesign>
</pnp:SiteDesigns>
<pnp:SiteScripts>
  <pnp:SiteScript Title="SPFx Install Script" Description="SPFx Install Test design" JsonFilePath="siteScript.json" />
</pnp:SiteScripts>
</pnp:Tenant>
<pnp:Templates ID="CONTAINER-TEMPLATE-A1920ECC06974C97BADCBF09B1260DE6">
<pnp:ProvisioningTemplate ID="TEMPLATE-A1920ECC06974C97BADCBF09B1260DE6" Version="1" BaseSiteTemplate="GROUP#0" Scope="RootSite" />
</pnp:Templates>
</pnp:Provisioning>

Run these PowerShell PnP commands:

Connect-PnPOnline -Url https://zergs-admin.sharepoint.com
Apply-PnPProvisioningTemplate -Path ./PnP_TenantDesign.xml
$script = Get-PnPSiteScript | Where-Object {$_.Title -eq "SPFx Install Script"}
Get-PnPSiteScript -Identity $script.id | fl

You will see that {AppPackageId:SPFxInstall} token is not replaced

Content : { "$schema": "schema.json", "actions": [ { "verb": "installSolution", "id": "{AppPackageId:SPFxInstall}" } ], "version": 1 }

Expected behavior

When running these commands

Apply-PnPProvisioningTemplate -Path ./PnP_TenantDesign.xml
$script = Get-PnPSiteScript | Where-Object {$_.Title -eq "SPFx Install Script"}
Get-PnPSiteScript -Identity $script.id | fl

We expect to see {AppPackageId:SPFxInstall} token replaced with an actual ID of the app that is available in the App Catalog.

Actual behavior

As a result, when applying the new site design, step responsible for installing SPFx solutions fails with an error:

2019-07-23T14:20:05.8810780Z Title OutcomeText Outcome 2019-07-23T14:20:05.8811469Z ----- ----------- ------- 2019-07-23T14:20:05.8811797Z Install SPFX Solution Something went wrong and we could not complete

Steps to reproduce behavior

See complete example here: https://github.com/Zerg00s/PnP-Site-Design-SPFxInstall

Which version of the PnP-PowerShell Cmdlets are you using?

[ ] PnP PowerShell for SharePoint 2013
[ ] PnP PowerShell for SharePoint 2016
[x] PnP PowerShell for SharePoint Online

What is the version of the Cmdlet module you are running?

3.11.1907.0

How did you install the PnP-PowerShell Cmdlets?

[ ] MSI Installed downloaded from GitHub
[x] Installed through the PowerShell Gallery with Install-Module
[ ] Other means

pnp / PnP-PowerShell