This sounds like they implanted the grafts facing straight up rather than facing forward. Hair doesn't grow straight up out of the scalp in most places. It's usually angled forward in the front half while also facing towards the sides a bit on either side of the hair line.
I think most people comb their hair back because they get less grafts transplanted into the midscalp and crown, so combing it back usually provides the best coverage. This is not always the case, though. There are a lot of people who do side parts.