I got 3 lights running Anduril2. About to dnld to a HK04. I did some light rev engineering on the HK04. They use a 3 leg part (FET?) with resistors preceding it to implement the single 7135 channel. Turns out they precisely reproduced 0.35 amps with the circuitry! I tested it simply by lots of measured ramping over the first flicker - seems pretty dead on averaged to 0.35 amps.
The HK04 driver uses 2 large/typical FET's in parallel for the main FET channel, and has switch LED's, and USB-C charging. The charging appears to share the one color switch LED, and uses another switch LED - I think they are green and red. I destroyed the switch PCB in getting it out so am replacing it, but don't have a 2 color (4 wire) switch PCB to use, so not supporting the 2nd color for charging. The one I'm suing though has 4 LED's but all wired together.
So even though it's a custom ATTiny85 based driver, it looks like a FET+1 with 1 color AUX/switch LED's to the firmware. Interesting...