It's possible now to download a backup that doesn't fully complete, might time out or something. If you put something at the end of the file like BACKUP END, not only would we know it's complete when looking at it, but there could be some sort of check to see if the backup was complete.
If backups are timing out than having a corruption check isn't going to fix that. The user should talk to their host about the timeout.
You can run a backup from the command line (mysqldump from cron job) and it will show you any errors or if tables are skipped. I also setup all my scripts to do an uptime at the beginning and end so I can see how long it took and the CPU usage but to also make sure it completed fully (if the last uptime is missing then I know it didn't).