Nothing wrong with carbon steerer; got full carbon forks on my best road bike, can't recall the brand (Izumo or am i making it up?) but they came with x-ray photo of the crown/steerer area.
also remember you need to use expander type bung, not star-fangled nut.
the lower race due to the alloy insert needs the steerer to be thinned down - can you see or feel if the steerer is thicker internally at that point to compensate - I would expect it to be.