It's way easier than it sounds. Logitech provides a tool that lets you program their gaming mouses. They use Lua. I don't know Lua but there were plenty of guides for different gaming macros like recoil compensation and the Logitech documentation was decent enough.
This is making me feel old. Totally agree it is difficult, but not impossible.
Logitech is the problem here for even allowing this in the first place. No CRC checks for mouse firmware or anything? It screams poor implementation. I will not be surprised if anti-cheat software starts banning people or companies like Logitech.
Kind of sad to see the number of threads and communities online encouraging this. The point of games is to have fun, when you cheat all that goes out the door.
There are multiple mice vendors that allow this. And you can’t ban them because the cheater focused ones will just set their device ID to match some common device.