Windows 10 / Intel HD Graphics 630
Short description of error
Using the "Active Editor Only" should only give you playback in the viewport in which you have your cursor hovering over, this doesn't seem to work.
Exact steps for others to reproduce the error
Split the 3d viewport into two parts
Animate the cube moving a bit over some frames
Go to the Timeline and open the Playback menu
Check "Active Editor Only"
Uncheck "All 3d Vew Editors"
Uncheck "Animation Editors"
Hover the cursor over one of the 3d viewports and hit play (SHIFT+Spacebar)
...it plays both 3d viewports instead of only the one you're hovering over...