Thanks for your response. It just seems like there should be a way to share fitness info within the same Apple ID. I’ll bet there’s plenty of spouses that don’t establish separate IDs that can share in somehow. Anybody??
No. There is not a provision in Apple ID for a single account to have sub-identities. There's no way for the system to know that an iPad signed into
fictitiousappleid@domain.realm is used by someone different than an iPhone signed into
fictitiousappleid@domain.realm. (And it's not a safe assumption to say that an individual will only have one iPhone signed into an account at a time - most people have their old iPhone and new iPhone signed in at the same time during the setup process.)
Yes, there are ways to work around that limitation in certain areas, like iMessage/FaceTime's Send & Receive settings, and the Apple TV device/tvOS has a provision for multiple user profiles so each family member can customize their viewing preferences. But Health in particular (and Fitness is part of Health) is designed to be especially private/personal, in keeping with legal requirements for personal health/medical information. As with other iCloud features, if Health is enabled in iCloud settings on your iPhone and your wife's, your Health/Workout data is going to be merged.
Apple changed its approach to the sharing of Apple ID accounts quite some years ago. They recommend that each family member have a personal Apple ID, and that the family use Family Sharing in order to share their iTunes/App Store/Books/etc. purchases and subscriptions. This gives each person a unique identity for iMessage and FaceTime, their own 5 GB of free iCloud storage, can store data in iCloud without the possibility that another family member may accidentally (or maliciously) delete something or merge their data with yours....
Bottom line, Apple doesn't want to facilitate the sharing of a single Apple ID, so there is no provision for sharing workouts in the way you desire.
Yes, it can be a royal pain to unravel/separate shared data if you choose to go the "personal Apple ID" route after sharing for so many years, but in the end you'll have fewer sharing-related problems and workarounds.