NYJack-
The 12.5 rollout was said to begin on Sept 12. Yours is only the 2nd report I've seen of anybody having received it.
Rollouts are done individual Roku installation by individual Roku installation, with an update schedule known only to Roku. If you have multiple Rokus, they may not become eligible for the update at the same time, even if they are the same Roku model.
Roku menu path Settings > System > System update will show you your current Roku version number. Down in the lower left corner of this screen it will also show you when your last update was installed.
I haven't seen 12.5 yet myself, but I think the display of the Continue Watching bar and choice of 3x3 or 4x4 channel grid are supposed to be options listed in Settings > Home screen. In the past some Roku updates have just set the stage for features that were added later - I don't know if that is the case here.