One is seasoning aromatics, the second is making a more even veg coating than seasoning at the end does; stirfry vegetables at a high heat won't release water t

One is seasoning aromatics, the second is making a more even veg coating than seasoning at the end does; stirfry vegetables at a high heat won't release water thus won't have a 'sauce' to carry seasoning across the surface, this method makes it more even.