If you click inside a Dialog or SideSheet component, drag your mouse outside of the element to the overlay, and release the mouse, the dialog / sidesheet dismisses.

Steps to repro:

1. Go to https://evergreen.segment.com/components/dialog
2. Click the first Show Dialog button
3. Click inside the dialog, and while holding down the click, drag your cursor outside of the dialog to the overlay
4. Release the click
5. Notice that the dialog is dismissed

I'd expect the dialog not to respond to the dismissal because the click didn't start on the overlay.