Immediately after creating an Entity and its attributes, what is the expected behavior when using...

You cannot use the bootstrap data from Excel. You are required to Publish the module first.

The bootstrap will try to automatically map the Entity attributes with the existing headers, in the first row of the Excel file.

The bootstrap only works all attributes match exactly the headers on the first row of the Excel file. Otherwise you get an error...

You cannot use the bootstrap data from Excel, because the structure of the Entity is already defined.