Why surprising?
Your Humax is the latest generation, unlike my original Foxsat and Foxsat HDR, so surely would be expected to be faster and more responsive than older Freesat makes/models/variants?
Not necessarily... the latest Humax'es use a web-browser for the UI (all coded in HTML5), whereas I think the originals used a native-language UI process.
My 1010S feels slower than the FoxSat HDR, but I believe this is mostly due to attempts to use visual effects for scrolling rather than just updating the screen...
So even though the main CPU core on the SoC has gotten faster, the graphics requirements for the UI has become heavier.
But it's all a trade-off between making UIs quickly and bug-free, and performance.
Remember the smoothness of those old arcade games? (or even some of the games on microcomputers of the eighties...)
Took a loooong time to code properly - would be very expensive to do, QA, and maintain these days.