It depends on what you mean by "feature parity." jj has some features git doesn't, and git has some features jj doesn't. That's likely to be the case into the future, for sure.

There's also like, some features of git aren't features in jj, but that doesn't mean you can't do that stuff with jj, it just works differently. The index or stashes, for example. In a literal sense, that's not parity, but in a logical sense, it is.