[projektfu]

Generally, EDI doesn't really contain the bits about telling another system what to do. You could build an API on a base of EDI data/document types but there will still be missing bits about semantics and protocol that will have to be filled in by your API description.

If the API is "put EDI files into this directory on the FTP server" then, yeah, it is an API of sorts. Presumably there is an automated batch process that reads the files and perhaps generates responses.

I think what people are asking for when they want API rather than "just EDI" is that they want something their software can use, that gives results and error codes they can understand, so that they can orchestrate and debug the process. Also, they probably want something they can implement without paying thousands of dollars to an intellectual property holder just so they can read and write the messages.