> The only reason to not use it, is because some of those Apps are built with third party multi-platform frameworks and not UIKit (React)

Anecdote: I’ve worked on a few large iOS teams at well-known companies. At all of them, we have moved toward building UI in code and specifically banning the use of XIBs and Storyboards (we still use all of Apple’s frameworks — e.g. UIKit). Part of the reason is merge conflicts — in much the same way that merging Xcode project files requires every engineer to understand and be able to parse the syntax when looking at a diff, merging changes in XIBs and Storyboards is fraught with danger (at best).