Purpose of capacitor and resistors on the output of three-state buffer
The datasheet is showing you the test circuit they used to test the buffer.
The propagation delay are specified into a certain CL.
The output enable and disable times are specified with a certain CL, RU and RD.
If your circuit stray capacitance and load capacitance are less than CL, then you should get at least the specified performance from the buffer.