I am running a customised version: OpenWrt SNAPSHOT r7314-c4aadbdaf6 / LuCI Master (git-18.176.34901-0d9a64b). Description can be found here. I installed the latest snapshot factory.bin (18-06) and then did a sysupgrade with the customised version. I used to do cat /sys/kernel/debug/gpio to see whether gpio is listed (I switched only recently to 18-06, before it had been 17-01). The slider never had an effect as you described. The file and its debug-directory in 18-06 do no longer exist.
I have no clue how to see the files like the script you linked. How is it possible to "extract" a .bin file?