Facebook may have cached the old version.
Use their debug tool to paste your URL and force Facebook to refresh their cache. After that your Facebook page should show the new heading/intro.
But I have never shared that page in Facebook before. I am 100% sure, because I have created the page recently.
I have created an article with content like Heading,Introtext text and published it. Then modified the same page with modified heading and Ingress and published it. I then share it via social reach example facebook. In my facebook page I am seeing the old heading and introtext instead of new ones.