Wholegrain has more dietry fibre and nutritional value than most multigrains which are often white breads with seeds in them.
The bran and the germ are the most nutritious parts of wheat (it contains vitamin B1, B2, B3, E, folic acid, calcium, phosphorus, zinc, cooper, iron and dietary fiber) and when the wheat is refined into white flour those nutrients get filtered out.
White bread and multi-grain that is not made with wholemeal have more simple carbs so they are absorbed faster and provide a sugar spike rather than longer lasting energy.

When you're put on the special low residue/low fibre diet for a colonoscopy you're allowed to eat white bread with the crusts off during the phase that you can eat solids.