From a career capital standpoint, it's a good way to learn how to research and write memos and how to navigate the U.S. government. Learning those skills, obtaining a security clearance, developing cross-cultural competence, and gaining visibility into a variety of selective government career tracks in a few years is hard to beat. Even if one were to be assigned to a country or two of relatively low strategic priority rather than one (say, China) of very high priority from an EA perspective, I'd bet it's a good career to explore for an EA. Depending on the quality of assignments staying in the FS can become a very high impact track for a decade or more. Here is an example of a high-impact FS career in the '00s-'10s.

This is an interesting question. I'd be interested to hear more about it, if you find anything!