>Now I'll have to maintain markup/presentation/logic in the same place
Only if you're doing it wrong. Presentation logic and markup will be in the same place sure, that's a good thing, but any application logic not dealing directly with displaying dom elements shouldn't be in and among your presentation code. Your concerns are separated and your presentation code is in the same place, like you would logically think they should be.
I have watched React Native talks in which they were advocating for this and bluntly calling it proper "separation of concerns".
But when you say that presentational markup and logic should be grouped together, doesn't this mean that we have to divide our js files even further to separate business logic from presentation or view logic?
Only if you're doing it wrong. Presentation logic and markup will be in the same place sure, that's a good thing, but any application logic not dealing directly with displaying dom elements shouldn't be in and among your presentation code. Your concerns are separated and your presentation code is in the same place, like you would logically think they should be.