Why Slack is no longer using a cross-platform C++ library

"We were spurred to write an update when Dropbox published this post about why they also decided to stop using a C++ library in their mobile apps."

I was about to ask why this was being re-published... and also makes me wonder about if there are use cases where C++ for cross-platform makes sense and has been a huge success. To make a callback to AirBNB when they ditched React Native, they made it clear that they weren't saying that mixing React Native and vendor-native code wouldn't work for everyone, it just didn't work for them.

> Objects from DataProviders are returned as immutable models. On iOS, where the app uses a CoreData cache, this means the rest of the app no longer needs to access mutable CoreData objects directly, which reduces the need to worry about concurrency issues and avoids the crashes due to accessing data on the wrong thread that are common with CoreData.

Is this the common way of dealing with core data? I am actually doing exactly that at work right now, and was wondering if it was the right decision.