Unfortunately, Stryd only offers syncing planned workouts (e.g., from its training plans) on the Apple Watch and Garmins. For Suunto, Polar and Coros, Stryd only supports importing activities into its platform after the fact.
More information can be found here: https://help.stryd.com/en/articles/6879452-can-i-do-structured-workouts-on-suunto-or-polar#
I think that this is a pity!