One solution (until I create a bridge where Yoast talks to Sections) is to turn Sections off, and click the “Send Sections to Editor” button.
Then turn Sections back on.
This will send all of your Section content to the default editor so Yoast can analyze it.
Other than this one issue with Yoast, Sections is great. I use it on this site on almost every page – not sure what I’d do without it! 🙂
Let me know if either of you have any questions.