Axon generates dynamic multipart responses with boundaries and headers to bundle files specified via query parameters. sendfile handles "serve this specific file" but does not handle "bundle these N files into a multipart response."
For static file serving, sendfile would be the better choice.
Reading the manpage for sendfile leads me to believe that it can be used for that purpose
I might be wrong then! I'll make a note to take a look. Thanks for pointing this out.