pako

I am not 100% sure that I will answer this question accurately and truthfully.
In my opinion, the BCM numbering on Orange Pi boards makes no sense (I don't use it myself in principle). This only makes sense for Raspberry Pi boards (BCM is short for Broadcom - the manufacturer of the SoC on RPi boards).
OrangePi.GPIO is "RPi.GPIO drop-in replacement library for Orange Pi Boards" and its original author (Jeremie-C) apparently wanted (for Allwinner SoC boards) to maintain some degree of compatibility with the original RPi.GPIO library.
I actually only made a fork (but extended and fixing some bugs) of the mentioned Jeremie-C project and I did not change the numbering methods introduced by the author.
I prefer to use BOARD numbering, which in my opinion makes the most sense (e.g. it greatly facilitates the portability of code between different Orange Pi boards). SOC numbering can also be beneficial in some cases. The SOC number of a GPIO pin can be easily calculated if you know the pin name (like PH18). You can find the procedure here.
Or you can use the "GPIO" column from the table for the relevant OPi board from this page.

I return to this old topic.
Perhaps someone will be interested in my contribution.
I have successfully modified the library https://github.com/Jeremie-C/OrangePi.GPIO, so it also works for H6.
You can find the modified library here:
https://github.com/Pako2/OrangePi.GPIO.

I return to this old topic.
Perhaps someone will be interested in my contribution.
I have successfully modified the library https://github.com/Jeremie-C/OrangePi.GPIO, so it also works for H6.
You can find the modified library here:
https://github.com/Pako2/OrangePi.GPIO.