Not really, it is implemented also in Object.

It is used to script brick layout properties. So user can say:

brick height: 10.

brick height: #approximate.

brick height: [ :b | b width * 2].

or even

brick height: HeightStrategy new.

so brickValue: is sent to any kind of object that is used as height. So without changing brick itself user can implement its own class and override brickValue: and have custom strategy to calculate height.

Such practice is used in many places in brick.