Ask HN: How does my new ISP "leak" my geolocation?

Since I moved to a new ISP, I've noticed that both Google and Amazon are now able to better geolocate me (Amazon even lists the correct pin / zip code). With my older ISPs, Google and Amazon sometimes even listed other cities or wrong pin / zip code within my city. I have disabled geolocation on both my browser and os (with a firewall) and don't believe that is the source. Moreover, I tested with a cellular hotspot connection too (which is from a different company) and Google and Amazon aren't able to determine the location accurately with them, as they do with my wired ISP. So what could my new ISP be doing different that it "leaks" my geolocation so accurately?