Delta query for group properties not accurate for classification changes - azure-active-directory

Question

We enforce base controls to Office 365 groups that are dependent on the data classification value. We have two ways these controls get applied:
Through a Graph subscription which automatically applies a set of base controls to an Office 365 group
A full scan to ensure each Office 365 group with a data classification value is assigned the correct base controls
We are trying to make the 1st option execute more efficiently by only proceeding with checking/applying the base controls if the data classification property changes. The delta query for group appears to be bugged; if the classification property changed values, it does not correctly report this. Any property that has been changed has a "null" value. Also the visibility property is always there.
Repro steps:
1: Initialization. Get delta token.
HTTP GET https://graph.microsoft.com/beta/groups/delta&$deltatoken=latest
2: Make a classification change to an Office 365 group. Make a description change to another Office 365 group.
3: Delta Query.
HTTP GET https://graph.microsoft.com/beta/groups/delta?$deltatoken=DeltaToken
Prefer:return=minimal
Response is:
{
"#odata.context": "https://graph.microsoft.com/beta/$metadata#groups",
"#odata.deltaLink": "https://graph.microsoft.com/beta/groups/delta?$deltatoken=NextDeltaToken",
"value": [
{
"classification": null,
"description": null,
"visibility": null,
"id": "Group1ID"
},
{
"description": null,
"visibility": null,
"id": "Group2ID"
}
]
}
Edit: Forgot to add... Microsoft docs mention a null value means the value is empty or the property has not changed. This observation doesn't reflect the docs.