I'm sure they can't be there to 'save water', as they auto flush as soon as you stand up, knowing good and well you still gotta wipe your ass and flush again anyways...
I'm trying to figure out how you trigger auto flushing just by leaning over. Meanwhile, auto flush on most public toilets I've used has a 50-50 shot of just not working at all, so I have to find the manual button.
At least for me, I know that I have a small butt and don't sit all the way back against the seat (there's quite a lot of space), so often these sensors don't catch me in the first place. Do you lean so far you move away from the sensor or something?
Regardless, both of us have relatively unique problems, I think. These sensors have been tuned to the average ass.
Well I'm not sure what sort of sensors they tend to use in your area, but the sensors here aren't looking for your ass or weight on the toilet. Here they use a wall mounted sensor that apparently tries to detect your back and I guess the distance of your back to the wall.
If you're not sitting almost perfectly upright (as in leaning forward to get some toilet paper), the stupid thing thinks you done got up and triggers the auto-flush.
Not like I expect anyone in the comments to be any sort of plumbing/sensor expert, but the systems and sensors around here are usually made by AquaVantage/Zurn, if that makes any bit of difference.
Oh, and no I don't even have to lean very far forward to reach the TP, just leaning forward roughly 6 inches seems to be enough to trigger the stupid thing.