@Kelly149 Yes, you missed it- there was a thread Lizzie started, asking if hosts used the email feature, to which many responded yes, it was essential in order to send attachments, However, following their M.O., Airbnb ignored that and eliminated it, unless, as you say, you "attest" to only using it in the ways that Airbnb, in their limited imagination and knowledge about hosting, could conceive of.
I do use it, and need it to send my guests a map to my place. Although half the time my guests got the email but without the attachment, so I have to ask them for their actual email address.