11 points
Without any prior knowledge if a trailer for Portal: Prelude were released today it would be equally as confusing. The flash version wouldn’t be since it would be strange for Valve to make a flash version of anything officially, so that’d set off flags, the Half-Life ones likely would be confusing as well, purely from a “released a trailer with a very clean logo and the word official in the title” standpoint, not really a general product naming standpoint, but that series is more dormant, so maybe it’s less likely to be confusing.