Transactional push notifications API

We urgently need to set up transactional push notifications and our architects and devs have been looking into the documentation 
https://experienceleague.adobe.com/docs/campaign-standard/using/communication-channels/transactional-messaging/transactional-push-notifications.html?lang=en

https://experienceleague.adobe.com/docs/campaign-standard/using/working-with-apis/managing-transactional-messages.html?lang=en

However, once we were testing the API, it appeared that it is impossible to send bulk transactional messages via API, that the calls to the API are done one by one. Is there a solution to it? using sFTP and files seems like a workaround and it seems strange that adobe wouldn't be able to handle sending them in bulk. 
We are using adobe campaign standard.

Thanks in advance