Hello Dan Dorey,
If I understand correctly, this benefit or any other benefit or restriction applies to all resources under the subscription based on the subscription offer type. Therefore, you can simplify the request by returning only VMs that are allocated under subscriptions with the offer ID ms-azr-0023p.
There is the post on how to retrieve Offer Type of Subscriptions via REST API.
Hope this helps.
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Sincerely,
Olga Os.