The timer on the Watch Pro 2 is nearly useless as it is. The screen stays on the entire time and locks you to the timer screen. Literally the first time I tried to use it something must have bumped it and my time was paused. Also the single weak vibration is not nearly attention grabbing enough.
Meanwhile the stopwatch works perfectly, you can leave the stop watch running for as long as you like in the background with no issues.
I use the timer function on my watch pretty frequently and with how it works on the watch pro 2 It kind of kills the whole thing for me.