Consider a widget that rebuilds very often (typically because of an animation).
Then consider editing the sources of that widgets through hot-reload.

It seems that when doing so, there's a chance for build method to be called before reassemble was, but with the updated content.

This is a big issue for the following open source library: https://github.com/rrousselGit/flutter_hooks
As it needs to override the reassemble behavior to handle potential changes within build method.

But if build method is called before reassemble, then the library won't be ready for it and the app will enter into an invalid state.