How does SBIE let .msi program uninstall to detect that files are not occupied?

[lmou523]

In sbie, install an msi program, open it, and uninstall it (while the file is occupied).
When uninstalling it doesn't seem to pop up a dialog box that the file is occupied and lets you close the process.
How does it do this?
@DavidXanatos

[lmou523]

A dialog box should first pop up outside the sandbox, giving you the option to close/not close the process
When deleted later, it seems that the changed file will be deleted regardless of whether it is occupied (this is estimated to be Microsoft's driver in the assistance).