It is not only the brakes but the suspension. If you compare say my W126 to a W220 for example:
The W220 has larger front discs with bigger calipers, maybe 4-6 piston's? never counted.
They are also cross drilled.
The air suspension keeps the car extremly flat during hard stops.
The traction control uses every ounce of grip the tires can muster.
So it stops insanly fast, perfectly straight and will throw you into the dash while the car stays level!
Auto makers have not been sitting still for the last 25 years.
Not that W126's have bad brakes, I love the brakes on my car they are great! Tons of bite and the bleed off speed real fast.