I can't speak for the author, but it may be for simplicity's sake. Personally I would have still have gone Babel+* but a Babel transpilation pipeline adds a no

I can't speak for the author, but it may be for simplicity's sake. Personally I would have still have gone Babel+* but a Babel transpilation pipeline adds a non-negligible level of complexity to a project, especially when it comes to debugging/performance optimisation.