Why did the datasheet mention this interface?
From the datasheet:  


  The FSMC can be configured to interface seamlessly with most graphic LCD controllers. It
  supports the Intel 8080 and Motorola 6800 modes, and is flexible enough to adapt to
  specific LCD interfaces. This
  LCD parallel interface capability
  makes it easy to build cost-
  effective graphic applications using LCD modules with embedded controllers or high-
  performance solutions using external controllers with dedicated acceleration.  


Its mention under memories is an error. (ST documentation sometimes has inaccuracies.) The 8080/6800 reference refers to the control signals. The 8080 for instance has an ALE (Address Latch Enable) to allow address/data muxing. The 6800 bus is not multiplexed, it only needs an enable and read/write signal.