There are few questions about some time between GUI copy window finishes the copying process to the external drive and a moment when the IO queue is fully written to the drive.
IO queue: https://askubuntu.com/a/428529/404171
This is why USB safe eject doesn't work for some time until data is written. Debian/Ubuntu shows notifications when it is not allowed to eject the drive, and when you can eject it. Windows (afaik) at least waits for the IO queue to empty when you click "Safely eject drive" from the status bar. We all know, that the situation may lead to the corrupted and half-written data on the drive.
The question is - when you suspend the computer during the copying phase, when GUI reports success, and IO queue still writes the data to the drive - does it respect the IO queue? Or that could also result in corrupted data?