Hey, @w-works !
I appreciate you joining the conversation.
You’re right - Shopify’s free themes, including Boundless, are designed to display the featured image for a page when you share that particular page link on social media; if you’re posting a link to a product page, then the product image should appear as the featured image.
That being said, the image that’s used is also dependent on the social media platform you’re sharing your link on. In the event that the social media platform cannot pull an image from the product page, then the image from Online store > Preferences will be used.
Which social media platform are you sharing your product links on? Do you have an example of a link that you can share with me?