The page notes that in 2023, Google will launch Google accounts for Fitbit, mostly for those who sign-up for Fitbit service or activate newly released Fitbit devices.

After we launch Google accounts on Fitbit in 2023, some uses of Fitbit will require a Google account, including to sign up for Fitbit or activate newly released Fitbit devices and features.

If you have a Fitbit account, after the launch of Google accounts on Fitbit, you’ll have the option to move Fitbit to your Google account or to continue to use your existing Fitbit devices and services with your Fitbit account for as long as it’s supported.

To recap, Google will start forcing some Fitbit users (mostly new ones) to use their Google account to sign-up for and activate Fitbit devices in 2023.