The assistance is there, but it doesn't enable you to truck up huge hills super fast -- it'll give you enough of a boost so that you're not completelyannihilated, but doesn't do all the work by a longshot.
This makes sense for such large files, as a means to cut the downlink time and save your capped data plan from getting completelyannihilated in one fell swoop, but don't be expecting to get the best possible quality from it.