How to reproduce:
1. Open the attached "ReimportCheck.zip" project
2. Once the Editor is open, drag any file over the project pane from an explorer window

Expected results: InternalEditorUtility.isApplicationActive returns false when the file is dragged over
Actual results: InternalEditorUtility.isApplicationActive returns true when the file is dragged over

Reproducible with: 2017.4.31f1, 2018.4.5f1, 2019.1.13f1, 2019.2.0f1, 2019.3.0a11

Other examples where InternalEditorUtility.isApplicationActive returns an incorrect value:
1. When you select another window while Unity Editor is loading and is still on the splash screen, upon loading InternalEditorUtility.isApplicationActive will return true although the Editor isn't focused
2. If you minimize the Editor by clicking the icon in the Taskbar, InternalEditorUtility.isApplicationActive will start returning true after 2-3 frames although the Editor is minimized
3. If you alt+tab while a saving a scene, after saving InternalEditorUtility.isApplicationActive will return true
4. If you change windows while a script is still compiling

Note: The repro project contains code that will unset the AutoRefresh editor settings, this will affect all your Unity installs, so remember to reset this when you are done with the project