"are considering" might have been better wording, as the Sync developer hasn't decided yet. For RedReader it's pretty much guranteed to happen eventually as the app is open source.
Additionally, there is a Reddit to Lemmy API translation layer which could accelerate this.
It doesn't seem like the main developer has said anything yet, though, that's why I didn't include it in my list. But hey, it's open source, so I'm sure someone will contribute a pull request if it doesn't happen officially!