About a decade ago, removable devices definitely were mounted with the "sync" option on some distros. It really tanked write performance though, so perhaps that's why they changed it. Certainly Plasma (and probably most DEs; I only use plasma) will tell you when the device is fully unmounted when you use the udisks integration.
If I wasn't aware of what was happening here I likely would have just force shut down the computer after a minute of waiting. And I suspect if I had done that and checked the drive it would have appeared like the file was there, while actually missing part of the data.
1. Arch uses the "flush" mount option by default when using udisks (which is how removable devices are mounted interactively from a DE).
2. Manjaro has a package called "udev-usb-sync" that matches USB devices in udev and limits the write-buffer size. However, it appears to (by default, you can instead specify a constant value) calculate the buffer size based on the USB transfer speed, and given the fact that I have some USB 3.1 devices that cannot maintain 1MB/s of throughput while others that can maintain over 200MB/s of throughput and both report the same transfer speed to Linux, I don't know how effective it is.