Grasshopper preview visible in Rhino after closing GH window?

Rhino Rhino for Mac
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3

Actually, I don’t think I’m seeing this behavior. Let me triple-check. Indeed, I’m not.

Here are my steps to attempt to reproduce this:

  1. Launch Rhino 6 for Mac 6.17.19236.01022, start a new modeling window, and run Grasshopper.
  2. Place a Sphere component on the canvas.
  3. On the Grasshopper window, click the minus - button at the top left-hand corner to minimize the window to the dock. The Grasshopper generated sphere remains visible in Rhino.
  4. Click the Grasshopper window in the dock to bring it back.
  5. On the Grasshopper window, click the red x button at the top left-hand corner to close the Grasshopper window.
Expected Behavior

The sphere disappears.

Actual Behavior

The sphere disappears.

What are we doing differently, if anything?