The toilet flushing thing is performative. Even if toilet water usage were enough to be worth caring about, dual flush toilets use more water over the lifetime of the toilet, because the more complex designs have a higher failure rate: https://www.theguardian.com/environment/2020/sep/29/dual-flu...

Also, in about half of the country, aquifers replenish as fast as they are used, so there's no point in regulating their use. The largest concern is usually whether or not the well is contaminated.