Hi Leandro,
Your research is correct.
There is no direct prerequisite for SAP_BASIS on ERP from My Inbox.
Because My Inbox use TASKPROCESSING OData service which is a part of IW_PGW component in Gateway 2.0. Minimum prerequisite for Gateway is NW.7.0.
TASKPROCESSING service calls some of API or Function Module in SAP Business Workflow which is a part of SAP_BASIS component.
Supporting TASKPROCESSING services, several notes have been delivered in SAP_BASIS.
Go to the Note 2106212 - Release Information Note for SAP Fiori My Inbox.
There is a section for SAP_BASIS. Those are the pre-requisites.
Regards,
Masa / SAP Technology RIG