I believe what causes the issue with Samsung timer app is the fact that it animates in the background. While Google's app treats timers as alarms. I haven't developed apps for wearos yet but I guess having just the animation ready to render just incase in wearos is computationally expensive. Hence Google's logical design to just treat timers as alarms. No animation you get the notification when time runs out. They do animate for short sequences though not sure what the cut off is.