I played through the Pillar of Autumn about 3 times and couldn't unlock it and was worrying because everyone just seems to have it.
I firstly did coop on legendary, so we ran as fast through as we could
then i did easy solo speed run
then coop easy speed run
so it made me think i was just running too fast and missing the achievement trigger, so the 4th time i did the achievement for not jumping and took it very slow, stayed with all my marines and listened to all their dialogue and i got the achievement just as the elites and grunts come through the first pod :)
but it should be noted that this is technically missable!