1. Usually when you try to upload a file from the chest you get an error 0KB file, since the chest is protected storage nothing is able to work within or externally to it. Only avast can work within it to scan again, send to Alwil, delete etc. that is the purpose of protecting it.
2. the fact that it isn't the same name is showing that the chest changes it encrypts I believe, so nothing could possibly scan it without knowing the encryption routine, the same as avast can't scan encrypted files in its scanning.
If the file isn't zipped when you send it to avast, it may never reach avast! many ISP and mail servers use anti-virus programs if they detect a virus it may well be deleted. Zipping it and password protecting the zip file stops scanners from being able to scan it, they don't know the password.