Not seeing new start page for Safari on Catalina
I don’t know what you are seeing or expecting to see, but from what I see in Safari 13 on macOS Mojave, the favicon styles of Favorited websites look different. They are rounder and have a more transparent background. From a picture I saw about Safari in Catalina, it looks like it also has Siri suggestions below the favorites section. It didn’t look like there where any extreme differences.