The brakes are eddy current brakes, applying a braking force proportional to the speed of the train. These are fixed brake fins with no active speed control, the train slows until the braking force balances the gravitational force pulling it down the slope (which is why the brake run is sloped).

These rides generally don't feature friction brakes at all - they use a combination of fixed and moving magnetic brake fins and drive tires for the blocks - and I'm wondering if this ride should even get the normal brake pieces. It might be confusing if I call this piece "magnetic brake" if the regular brakes are also magnetic just with less realistic behaviour, but I do think it's worth having this special piece for this ride type, as they very commonly feature this type of brake run, and those brake runs are usually hit at speed so too sharp a deceleration looks bad.

Technically, the standard brake piece in game does also works like a magnetic brake, in that the braking force is proportional to speed - except that the force constant is so high that the train will very rapidly decelerate to the brake's speed setting, and getting a smooth deceleration requires you to fiddle with the speed settings individually. This piece is meant to provide a smoother, more realistic braking force.