The wiper and headlight sensor are the same. Just like my A4, there is that adjustment on the wiper stalk (as you pointed out).
There are 4 things that I have learned with auto wipers,
- Replace wiper blades more often then you think (water left causes wipers to keep going)
- Keep windshield clean
- Do not use the orange washer fluid (with rain-x)
- Rain/Light Sensors like any other sensor can fail
Specific to 3, there has been a known issue with that washer fluid that messes with washer fluid level sensors, and puts too much rain-x on the windshield. This can affect the sensitivity of the wipers/lights.
Specific to 4, there have been issues with the rain/light sensor even with OEM windshields. Another issue is when you do replace a windshield, sometimes the aftermarket sensor isn't glued properly (there are writeups on how to re-glue them on).
I have an aftermarket shield on my e46. I have zero issues with the wiper sensitivity (with the 18 yo OEM shield and now with the replacement). My headlights also are perfect, but I am ok with them coming on earlier than later.
There also is a known issue with the e46 Light Control Module (the switch itself), and unfortunately they are coded to the vehicle, so if you try to swap it yourself, it can trigger the tamper dot on the cluster.
Basically, I should have said, as long as your system is functioning properly (and it can function properly by fixing issues, which can get expensive), if you have auto headlights, one can survive without a physical headlight button.