Thumbnail not matching preview (Staff: By design)

In the filter editor sometimes the image shown as a thumbnail on a component does not match what is shown in the preview. Here are the circumstances needed to reproduce this.

1. In the filter editor create a rectangle that has bounds x 0.25 to 0.5. y 0 to 1 and no corners or bevel
2. Invert the rectangle to change it's color
2. Add an offset component that has offset X = 0.25, offset Y = 0 and XY Anchor Default (Size) to offset the inverted image
3. Blend together the original rectangle (foreground, 100% opacity ) with the offset rectangle and feed it to the result.
4. Open an image which is wider than it is tall ( I used 3/2 )

Click on result and note that the result shows that the two overlaid rectangles are of different sizes, note that the thumbnail image in the result component shows them being the same size.

I believe that the preview is correct and the thumbnail is incorrect, in any case it makes the thumbnail not at all useful if it does not match what the filter is doing.

This is by design (not very obvious, I admit).
Please note the thumbnail is square and the preview reflects the actual rectangular image. The culprit here is Free Rectangle: if you set the XY Anchor to Default (Size), the preview and the thumbnail will match.
https://www.filterforge.com/more/help/...Works.html