I haven't actually read a magic rulebook since revised, so all my knowledge of the current Magic ruleset is based on what people have told me have changed since then.
But, yes, the attacker has always decided where damage is dealt. In older rule sets, you could assign all of
War Mammoth's damage to bear A, delivering 1 trample damage while in the current rule set you can't do that. I assumed it was because you had to deal lethal damage to each creature first, but it may well be due to some change in how trample functions. Its pretty much moot, because the only time it would matter is if they double blocked with
Hornet Nest can something else you could deal all the damage to the something else and avoid the tokens.