available in 1,800 cities doesn't mean coverage in 1,800 cities - a lot of venue coverage is being counted

There's a lot going on there like "5G service in city X!" where they really mean "we have an antenna mounted at the ballpark to cover a high density use case."

There's really 3 types of 5G: ultra-wideband, mid-band, and low-band. Ultra-wideband is the 5G you hear about most, with gigabit speeds but you have to be within direct line of sight to the cell site. There's also mid-band and low-band, which have similar ranges to LTE and can deliver a few hundred megabits instead of gigabits, and can handle problems like congestion better.