It's not weird, just different from the IRL standard. In AC brake bias is the percent of braking torque at each axle. So 75% front with 2000N of braking is 750N per front and 250N per rear tire. IRL they have physical leverage over the front and rear brake cylinders so it's the percent of pedal pressure going to each half of the system. Thus actual force at each wheel depends on the piston sizes (both master and multiple in each brake caliper), effects of any brake booster, friction coefficient (pad + disc material) and mechanical advantage (brake disc radius the pads hit)
AC skips simulating most of these because their end result (750N front, 250N rear) is exactly what irl teams are aiming for anyway.
Weight obviously transfers to the front on braking, if a car needs 75% front it's because it has so much load on the front tires. Not exactly surprising with sticky tires and aero that will bias towards the front of the car as it pitches forward.
Sorta like how IRL dampers would just be 0 to 20 clicks, not exact numbers, you set both by relative adjustments - need less rear? do that.