The TCU is still there with the HTG stuff, I don't know that it actually differs from the dkgecu version in that sense. I'm pretty sure the external controller just fires the solenoids directly or whatever. I've been shown a photo, picture the TCU board with about 13 wires soldered across it.
Yes, i have seen the wiring needed for the htg. It was initially why I did not pursue it further. Now that they are offering the modifications in house i have reconsidered. I had communicated with dkg a few times and it really didnt seem like they had or were interested in working on anything that didnt also have a standalone engine ecu.
You may be right about the function of the dkg being the same as the htg im not entirely sure of the method they are using.