This was by virtue of WebKit itself being (relatively) small and fast. I don't know what they call "the core component", it is quite misleading.
I used the last version of Uzbl in an old Debian container to debug a game I made specifically supporting the iPad 2, which is quite resource constrained, because Uzbl was based on a similar version of WebKit. WebKit somehow had to fit the iPad 2 and still be quite fast, so Uzbl, which is very bare-bones, felt very fast indeed on a decent computer.
I was looking at similar browsers, apparently epiphany (Gnome Web) is the only remaining open source browser based on WebkitGTK+ that's still maintained. Last version of Surf was released in 2021, Midori is actually a Gecko browser which I need to check out [1]. I guess someone could contribute and update Surf or Uzbl or fork the old Midori.
[1] https://news.ycombinator.com/item?id=38047006