For WebHook updates on new membership changes (Membership.Status=20) the JSON message for the notification used to set the "Contact.ID" to the value of the contact, now it set's it to "0". I assumed this change was not the expected behavior as it makes this message useless (I would have to scan all members to find the new one). The documentation clearly shows that the Contact.ID is set to a valid value and no indication of a special case where it is set to "0" (https://gethelp.wildapricot.com/en/articles/1670-webhooks)

This is what it used to send to the WebHook endpoint (redacted and formatted for readability)
{
"AccountId": "123456",
"MessageType": "Membership",
"Parameters": {
"Action": "StatusChanged",
"Contact.Id": "111111",
"Membership.LevelId": "1472252",
"Membership.Status": "20"
}
}

Now it sends
{
"AccountId": "123456",
"MessageType": "Membership",
"Parameters": {
"Action": "StatusChanged",
"Contact.Id": "0",
"Membership.LevelId": "1472252",
"Membership.Status": "20"
}
}

Since it is a valid message and my code returns "200" support was unwilling to look into it further since it is "working." I was also able to reproduce it successfully with https://webhook.site/

Hopefully this will help anyone with a similar issues and that the API, from what I can tell, is "unsupported" in any meaningful way.