You do you just probably dont notice it. A page back another member who owns a S4 even admitted the scrolling is a bit lagging in comparison to the iPhone 5. But here are some sites reporting the exact same issue. Its well known on android, no matter the device,
Forbes is typically hit or miss, but he references work from a credible source, saying it is still upon review plagued with the scroll lag. Thats a android thing, not a S4 thing specifically from my experience.
As for the GPU thing, where you being sarcastic? benchmarks are posted right above you. iPhone 5 Clearly pulling ahead(last years flagship). IMO for a price tag that high that's unacceptable.