There's probably truth in what you say about the Russians showing restraint (ie. not using U.S. "shock and awe" tactics) to avoid provoking a panicked response by NATO, but I think it goes deeper. Russia didn't seek this war and certainly did not want any war with a people they consider brothers. Slaughtering Ukrainians on the battlefield pleases no one. The U.S. looks at the world differently. They have no "brothers." They are Americans, and everyone else is merely inferior. So kill 'em all and let god sort 'em out, as the U.S. Marines like to say.