Unable to create deviceHealthScript object via Microsoft Graph Rest Beta API

I followed the official Microsoft Graph docs to create a deviceHealthScript object using detection and remediation PowerShell scripts. However, I keep getting an error:

Invoke-MgGraphRequest: POST https://graph.microsoft.com/beta/deviceManagement/deviceHealthScripts
HTTP/2.0 400 Bad Request
Vary: Accept-Encoding
Strict-Transport-Security: max-age=31536000
request-id: 35504886-0ed7-4a01-9519-52746591a0d8
client-request-id: ecda70e9-e087-433a-8ed0-bf3469bcf46c
x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"Germany West Central","Slice":"E","Ring":"4","ScaleUnit":"004","RoleInstance":"FR2PEPF000003EF"}}
Date: Fri, 13 Sep 2024 09:48:03 GMT
Content-Type: application/json
Content-Encoding: gzip
{"error":{"code":"UnknownError","message":"Microsoft Proprietary scripts cannot be created via Graph","innerError":{"date":"2024-09-13T09:48:03","request-id":"35504886-0ed7-4a01-9519-52746591a0d8","client-request-id":"ecda70e9-e087-433a-8ed0-bf3469bcf46c"}}}

The PowerShell code I'm trying to use is:

# Define the script content
$detectionScriptContent = @'
If (Test-Path "C:\Proactive_Remediation_Test.txt" -PathType Leaf) {
    Write-Host "Exists"
    Exit 0
} Else {
    Write-Host "File Not Found"
    Exit 1
}
'@

$remediationScriptContent = @'
New-Item -Path "C:\Proactive_Remediation_Test.txt" -ItemType File
'@

# Encode the script content to base64
$base64DetectionScriptContent = [Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes($detectionScriptContent))
$base64RemediationScriptContent = [Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes($remediationScriptContent))

$body = @"
{
  "@odata.type": "#microsoft.graph.deviceHealthScript",
  "publisher": "Publisher value",
  "version": "Version value",
  "displayName": "Display Name value",
  "description": "Description value",
  "detectionScriptContent": "$base64DetectionScriptContent",
  "remediationScriptContent": "$base64RemediationScriptContent",
  "runAsAccount": "user",
  "enforceSignatureCheck": true,
  "runAs32Bit": false,
  "isGlobalScript": true,
  "highestAvailableVersion": "Highest Available Version value",
  "deviceHealthScriptType": "managedInstallerScript",
  "detectionScriptParameters": [],
  "remediationScriptParameters": []
}
"@

Invoke-MgGraphRequest -Method POST -Uri "beta/deviceManagement/deviceHealthScripts" -Body $body -ContentType "application/json"

Can someone please help me identify what I'm doing wrong or if it's possible to create this object via Microsoft Graph Rest Beta API?