You're not the first one to suggest this and also not the first one to be wrong about it. Despite many FTers claiming that to be true, if you looked at UAInsiders original thread (first post), then you would indeed realize that no, the backend is different. Hence the different flight results sometimes. IME, there's a lot more results that come up, and also, many partner options that I've never ever seen before on the old site (and I couldn't replicate on the old when you were able to easily shuffle between both.