The feature can be used to, for example, set the host name and avoid the need for a static IP address. Version 1.5 of the imager introduced download telemetry to get a view of which operating systems are the most popular. The advanced options menu lets users turn off telemetry collection.
The new installer is available on the Raspberry Pi Downloads page, or you can get it from a Terminal window using sudo apt install rpi-imager to install it on a Raspberry Pi.
The version 1.5 installer was only released in December, so users may not have tried that version yet. It brought a submenu for breaking operating systems into categories such as general purpose, media player, and gaming and emulation.
Raspberry Pi introduced download telemetry as part of a plan to ensure the most popular operating systems are easier to find in the imager's menu system. It does not collect a device's IP address. Telemetry is on by default, and the new advanced options menu makes it a bit easier to opt out than previously.
Raspberry Pi publishes the telemetry data it collects on its stats page. According to its stats on downloads over the past month, Raspberry Pi OS (32-bit) is the most popular OS with a 45% share among those who use the installer. It's followed by other versions of Raspberry Pi OS (24%), Ubuntu (13%), RetroPie (5.4%), and LibreELEC (3.1%).