There is nothing wrong with your 1 press outputting 1, 2, 3, 4, 5 and 6 all at once.
And there is nothing wrong with it outputting:
-- 1 on the first press.
-- 2 on the second press.
-- 3 on the third press.
-- 4 on the fourth press.
-- 5 on the fifth press.
-- 6 on the sixth press.

In the first example, it is no different from a macro which reads:

#show
/cast Shield Slam
/cast Revenge
/cast Shield Block
/cast Devastate
/cast Thunderclap
/cast Sunder Armor

Naturally, because of the GCD, neither the macro nor simultaneously pressing all of those keys will help you much.

And similarly in the second instance, you are physically pressing one key and getting one response. And your timing or delay is determined by you, not the macro/script/program.