There was recently another thread regarding strange behavior of Garmin synced weight:
Your info seems very valuable to understand what is going on.
From what I can tell with your info, the Garmin synced weight was logged in intervals after your workout. When you do a workout, the most recent weight is used for the calculations, and that can come from a wellness entry or a settings entry, depending on what is most recent.
Looks like at the start of your workout, the weight from Garmin was not yet available and thus the most recent from wellness was used for the calculations.
Final conclusion:
- or you entered your weight on Garmin after your workout
- or you entered it before but it synced only later and the timestamp from the sync was used to locate it in time. If the weight from Garmin comes with a timestamp from the entry, the weight in the wellness would be correct but the activity may already be calculated with the most recent from wellness because the more recent one from Garmin wasn’t synced yet.