Last update to this post - after emailing the support team, they confirmed what we already know that Gallery Blocks are not allowed on certain pages like portfolio sub-pages.
The final kicker, though, is that they told me "Circle members can add gallery blocks to all content areas in 7.1. This is one of the benefits to being a Circle Member." So this functionality exists AND is capable on 7.1....but only if you're a superuser. I am not interested, especially after how frustrating it was to format my portfolio properly, in becoming a Circle Member. Ironically, not having access to tiny features like this is making me look elsewhere for a website builder once my subscription is up. Disappointing all around.