First off are you serious!? Trying to justify your idea based of the fact that WRXs and STIs are faster than a Supercoupe is absolutely childish it is not a valid argument or justification. The top mound IC doesn't make and STI faster than a supercoupe there is a whole lot more at play there, the cars are so fundamentally different in many ways, a 2 door grand touring car to a compact economy sedan that's sole purpose of existing is merely to homologate the chassis and powertrain components for FIA legality to RACE. Both cars had such completely different engineering goals. Also consider there is likely about a decade of difference in technology between the two cars...
And for a legitimate logical reasoning... Ford had experience with small top mount setups in the past and I am sure if the pros and cons balanced out one way over the other there was a very solid reason for it. Also when thinking about top mounts consider the addition of drag and the fact a scoop has to be huge to make it effective because you have to make it tall enough to get out of the boundary layer of air to actually get moving air. In large part the benefits of a top mount on a positive displacement supercharged engine are null and void unless it were your only packaging option (such as a mid engine car or something) superchargers are in large part already cooler than turbos, they do not have lag and due to the positive displacement type that a supercoupe uses, also due to this long piping and big intercoolers aren't really going to contribute to lag. However supercharged engines like ours are susceptible to heat soaking the rotors and supercharger case which a top mount would amplify.
Subaru likely did top mounts for these reasons: its a rally car, they get badly damaged sometimes so the less stuff in the crash zone the better, your less likely to get an intercooler mounted up high clogged with dirt, mud, leafs, grass etc..., drag doesn't matter because rally cars are geared so low they rarely if ever exceed 130mph, its engine has a lower height due to being a horizontally opposed 4cyl thus there is room for it there and it allows short piping to reduce turbo lag. If you think about it given the intentions of an STI or a WRX it makes perfect sense why they did things the way they did.