I noticed the same thing as well. I mentioned here – appfinite.com/topic/recent-blog-posts-on-front-page-pagination/#post-12987 that I posted on the StudioPress forum but haven’t heard anything back yet. I’m sure it’s something that was changed in the Genesis Framework itself and not the child theme, but not sure what exactly.
It only happens when we use the portfolio as a homepage. Other than that, if you use it as a regular page the pagination seems to work fine. In the past it worked both ways.