[panarky]

I read the article and couldn't find any hint that previously encrypted data would be undecryptable by either branch of the fork.

Is there a real risk of this that I missed, or are you just free-associating off the term "backwards compatibility"?

[daveguy]

The article specifically refers to backward compatibility with RFC4880, RFC5581, and RFC6687. These specifications include encryption techniques. So no. I was not just "free associating". Please do not assume the worst, because it could be that you just haven't understood the implications of the article.