Sure, but now you’re on a plane and would like to grab something from your bag - headphones or a sweater or an aspirin. Do you need to pull the bag from the overhead bin, balance it on your chair while you unpack the whole bag? Or do you reach into your bag while still in the overhead bin and pull out the item you need?

Not at all -- there's no need to pack every single item into a bundle.

For me at least, the "bundle" is basically all the clothing that will be used at my destination.

Like any other packing situation, you'd keep a jacket, sweater, headphones, etc. outside of the bundle for easy access en route.