Selecting thumbnail size for an image has no affect on the output in image masks that are circle left or right

[BigActual]

But it seems to work on just a circle mask. You can find what I'm referring to by changing the mask for Dean's photograph in the author section on the latest post I created, authored by Dean. When I tried to make his image mask left or right, the image would not shrink to the scale dictated by the image tools within WordPress. If I chose thumbnail size it would still display at full size.

[d4mation]

This is expected behavior. The way that the Left/Right Half Circle masks have to work, the image has to span the entire height and width of the SVG Mask.

If you choose Left/Right Half Circle, it is technically by default within a column even if you do not place it within a Column Shortcode. This is because the entire Post Content is within a column.

This causes the SVG Mask to scale to fit its container in width if it is set to Align Center... which is the full width of the content when not placed within a Column Shortcode.

If you choose Align Left or Align Right, that causes it to properly use the Image Size rather than the Container Size for scaling.

This quirk is unavoidable in how the Image Masks have to work.