This board is designed to allow the use of the cheap TFT boards off ebay that have a parallel rather than SPI bus. That makes the speed bearable with an 8bit micro. The controller itself is fairly easy to interface and just needs a chip select and (contrary to the docs) RD and WR qualifying. It can handle the 7.37Mhz bus for all but framebuffer readback - which nobody ever uses anyway.

These boards also have an SD interface that seems to rely on resistors to feed 3v3 with a pull down by the CPU (ie the CPU switches the I/O pin between outputting 0v and input (hi-Z)). That bit is supported but not yet tested.

Some have a resistive touchscreen that is a large resistance between two of the control signals. That can't be used when you are directly driving the bus but does no harm.