SaaS Fulfillment API – Filtering by purchaser/objectId not supported

I am working with the SaaS Fulfillment API and need to filter subscriptions by purchaser/objectId. However, filtering is not supported for the Get list of all subscriptions endpoint.

According to the documentation: Get list of all subscriptions – SaaS Fulfillment API

The endpoint currently provides the full list of subscriptions without filtering options. Could you please confirm if there is any supported way to filter subscriptions by purchaser/objectId, or if this capability is planned for a future update?

This feature would be especially useful for scenarios where we need to retrieve subscriptions specific to a given purchaser without handling large unfiltered result sets.

Thank you in advance for your guidance.