Back in the days before digital tools, comic and manga artists would often create their artwork on a larger scale, usually around 150% of the final printed size. Nowadays, we can control the artwork's quality through file resolution alone. However, many artists still prefer working on a larger canvas as it's easier to handle within the app, and allows for more detailed artwork.
The beauty is that during the pre-press process, the scale can be easily adjusted to perfectly fit the final size. Experts know that scaling down (while not resampling), produces incredibly detailed, sharp and vibrant prints.