Hello @payton white
Subdomains are registered in azurewebsites.net domain automatically by Azure, when you create App Service.
Azure owns all DNS Zone azurewebsites.net so you cannot know what person owns subdomains.
As you do not have access to Resource groups in other Azure accounts you cannot get private data.
Here is privacy policy from Azure
https://www.microsoft.com/licensing/terms/product/PrivacyandSecurityTerms/all