He took on Grant and McBride specifically because they're Vitali's size. Short of like Povetkin there's not many other people who he could have fought to get rounds against someone that big.
If it works for some boxers than good for them. 'Moving', not 'running' can be great tactically, especially against the cement feet brawlers you must love so much. Slick boxers aren't fighting that way because they lack courage dip ****.