It's still powered by a coin cell so it's probably for power conservation reasons. Way cheaper to periodically power on the BT radio and sync steps to your phone than it is to constantly listen for notifications.

It's not just power, if it where, they'd fit a USB C rechargable cell in there.

Its still a cheap casio resin watch at the end of the day. If this where to be able to push/pull notifications, the watch would be completely different in cost, ui, marketing, etc.

It would go from being charming retro tech with modern features, to dime a dozen bloatware/fitness tracking hardware.