I saw this go by yesterday and found it interesting. My laptop (Hp Envy), left to its own devices, instantiates both an ACPI backlight control and and an Intel backlight control under /sys/class. Oddly, it is the ACPI backlight that only had a few brightness steps. I don’t remember exactly how many as I am not in front of that machine and I disable the ACPI backlight control. The reason I do that is because my Intel backlight gives me 4882 steps.
Not sure what you can do with this information. Maybe investigate whether ACPI backlight is available? and maybe it has more steps?