View.xml is inheriting image sizes from parent (so an optional field is replaced by the value of parent)

[quisse]

I want to resize my images to a width of 250px and keep the aspect ratio (so I'm not adding a height tag). Instead of resizing the image to the full height of the image, Magento takes the height for that image from the parent theme's view.xml. So "If your theme does not contain a view.xml configuration file, it will be inherited from the parent theme. If you add the <theme_dir>/etc/view.xml file in your theme, it overrides the parent’s file." is a lie?

Preconditions

1. Magento 2.1.9
2. PHP 7.0.25

Steps to reproduce

1. Copy view.xml from a parent theme and add it to new theme
2. Remove <height> tag from image
3. Resize images

            <image id="product_page_image_small" type="thumbnail">
                <width>250</width>
                <aspect_ratio>true</aspect_ratio>
                <frame>false</frame>
            </image>

Expected result

1. An image with 250px width which kept the aspect ratio without adding

Actual result

1. An image with 250px width and 90px height (as defined in the parent view.xml)
2. 

[magento-engcom-team]

@quisse, thank you for your report.
We've created internal ticket(s) MAGETWO-84055 to track progress on the issue.