I think all 7135’s are used in each mode. I’m not for sure if a dual channel was ever implemented with a 105c 8-7135 type board.
The fet+1-7135 board was derived from the 105c by comfchair’s idea. It wouldn’t be hard for someone to make that board into a dual channel, I just don’t know if anyone ever did. About the only gain to using a dual channel would be the ultra low moonlight from a single 7135. Which the “raptor claw” 350ma 7135 would work the best at.
Look at each of the 7135’s VDD pin. If they are all tied to one pin on the attiny then they all are on together. If one 7135 runs to a different pin then its a dual channel.
It can be seen in HKJ’s test.