I don’t think the summery page is the key because I’ve been clicking done and then after it uploads to Strava (I have LTE) and drops back to the main menu, I switch to the HR app to watch my HR drop. It’s ending the run that ends the “workout” session in Apple’s system and also triggers Fitness focus to end and this is where Apple (not WOD) starts tracking the recovery.
BTW, I also got the TTS crash 2 times before wOS 10.2 was released. Hasn’t happened since. I’ve been using WOD for 3.5 years and those were the only 2 times I’ve had it crash which is actually a better track record than my Garmin watches. Hahaha.
I agree that it is not the summary page because, as you say, the workout is saved to Apple's Health system when it is ended and that is when they start recording the recovery information. So it should be recording the recovery whilst the summary is displayed and will continue to record it regardless of what WOD is doing.
It sounds like watchOS doesn't record the recovery if you end the workout after your heart rate has already dropped. This makes sense from a logical point of view, but I can see why you want to start recording it when there is a pause, because pausing is often configured to be easier than ending, especially at the end of a race. They can always discard the recovery data if you resume the workout rather than ending it.
It is quite a special case scenario that is dictated by the fact that it can be hard to end a workout after a race if it requires looking at the screen.
With the Ultra you can configure 3 different button combinations, so you may want to make the Crown & Side Button option end the workout, whilst keeping the Action & Side Button combination for pausing/resuming. It is quite awkward to press both at the same time, but still doesn't require the screen to be viewed.
Or maybe configure the action button to Pause/Resume and the Action + Side button to end the workout.
With other Apple Watches there is only one physical button combination (side button + crown), so you can't configure separate physical buttons for pausing and ending, which is where starting the recovery on a pause would be particularly useful.