The post I replied to implies that iOS is (somehow) "artificially limited" to be unable to access FTP - or at least I interpreted it that way.

FWIW, I'm not convinced that "web-based" is a better alternative for read/write file access, assuming you mean file manager webapps. No OS can integrate those into the native file picker, so you can't avoid the inefficiency of manually uploading files after changing them. WebDAV works pretty well though, if that counts...