The upside of having the rear brakes lock first in gravel is that you will be able to steer. The downsides are that it will take a lot longer to stop and the rear of the car will likely pass you during the attempted stop.
How often will we experience a panic stop in gravel vs on pavement?
All cars since the mid 1930's have the braking proportioned so that the fronts do 75% of the braking and will lock first in a panic stop. Was Henry right with the Model A and everyone since wrong? Was Henry right with the 2 wheel brakes on the Model T?