Your runs and Apple Health
My Garmin run has no splits
Garmin Connect sends a run's distance, time and heart rate to Apple Health. It never sends the run's splits, its route or its cadence, and Why Not reads only what Apple Health has, so a Garmin run shows no splits rather than splits that are not real.
Your splits, route and cadence are always in Garmin Connect. On Activities, Open Garmin Connect takes you there.