This is not an error message, it's a warning message so you are aware of this. We give you the option to remove any auto-prepend scripts during restoration.
This warning CAN NOT be possibly printed at backup time. It is something detected at restoration time. Auto-prepend scripts can be set up by .htaccess, .user.ini or php.ini files which may not be present in your backup but present on the site you are restoring to. Showing you a backup time warning would only be based on what is the case on the site you are backing up, not the site you are restoring to. However, this is something that will only affect the restored site, i.e. it only makes sense to warn you at restoration time.
In either case, as I said, we give you the option to remove auto-prepend scripts by removing the .user.ini / php.ini files and resetting the .htaccess files in the Site Setup page (second to final page during the restoration). So there's really nothing else we can do. We already notify you about a potential problem and give you the tools to fix it.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!