I don’t know what the braking distance is

At 70km/h, 20.6 metres. For ordinary cars it's ~50m.

In a nutshell, a tracked vehicle has quite a bit more contact area with the ground, it's also kind of hard to lift the rear wheels up so you can apply a lot of break force before you start to skid etc. And Leos have the hardware to actually do that, there's a retarder in the drive train and additional disc brakes.

Have side views on dirt and on tarmac.