Why are RC9 parameters missing in the full parameter list?

I want to set RC channels 6 thru 9 to passthru, but I just noticed that there are RC1 through RC11 parameters in the list, except for RC9. Does anybody know why?

I’m using Arduplane 3.0.2 on an APM 2.5 board.

Hello? Echo echo echo,
Perhaps this forum is dead.
I just posted an bug report here as I can’t get channel 9 to be passed through:

It doesn’t appear in the parameter list as channel RC9 doesn’t exist as an output channel on the APM2.x. Due to some history with how the channels were labeled the APM2 has channels 10 and 11, but not channel 9.
Cheers, Tridge