It's mostly the US and a few other small markets that even have millimeter wave 5G NR. This is mostly due to the fact that FCC had not wound down analog broadcasts in time, and mmWave/FR2 was the only way to do 5G in the US initially, as lower C-band were not freed up until 2021. Deployments of mmWave exist solely due to the sunk cost of existing equipment and narrow use-cases like stadiums and concerts.

The article predates our current reality where C-band (3.5GHz) is available for 5G