Can I create a single subscription with the same bill-to site for multiple inventory accounts?

No, you can't create a single parent subscription for the same customer with multiple inventory accounts.

All the sites with bill-to usage are associated with the selected bill-to account. If the selected billing account has only one bill-to site, the application sets that value as the default.

For more information, see Create Subscriptions in the Using Subscription Management guide on Oracle Help Center.