As per the official documentation here Excel REST Graph API does not work with consumer platforms, we assume consumer platforms means personal MS accounts, but when we tested the app created with a business account to access the data of Ms personnel accounts, we were able to access it.
We were able to perform the following operations for the personal account
Read/write data to & from excel files stored in a personal one drive account
Create workbook session for files in personal account
Create tables in the worksheet of personnel one drive account
So I request the team to please throw some light on what does it actually means to not have support for the consumer platform.

