Seems weird to announce it as part of a version and then also as a rolling release. Seems like the message could be much clearer by saying it is part of the browser but may be disabled by default.

FWIW, I checked about:config. There's some options in here that seem highly relevant

  browser.tabs.groups.enabled              false 
  browser.tabs.groups.smart.enabled        false 
  browser.tabs.groups.smart.optin          false 
  browser.tabs.groups.smart.userEnabled    true

These are the settings I have by default that are not allowing grouping.

Changing `browser.tabs.groups.enabled` to `true` enables the feature. Though note that it can still be difficult to align them right such that they group. Presumably `browser.tabs.groups.smart.enabled` is the AI feature mentioned in the article. But I have no idea what `browser.tabs.groups.smart.optin` and `browser.tabs.groups.smart.userEnabled` are.