Orders created via the Admin API (using either the orderCreate or draftOrderCreate mutations) are associated with the Online Store sales channel by default. They don’t appear as native POS orders and won’t show up in the Shopify POS “Drafts” view. There is no supported way via the Admin API to create an order that is natively recognized as a POS order or to pre-populate the POS cart directly.
Have you looked into using the draftOrderCreate mutation?