Thank you Andrew for the question and Abigel for the precise answer. 

Agree with Andrew. This is not an improvement but so many steps backwards. The supporting documents are important to justify the invoices. The attachments are more for customers than us. What will I do looking at the documents when I still need to send it out with physical email.

The feature was simply working, there was no need to take it out. I've also provided the feedback. Hopefully QBO team listens quickly.