Given this Health data (active calories):
Tapping the button “Sync last 7 days” does seemingly nothing. The last 5 data points shown are not changed no matter how often you press either one of the two sync buttons.
Despite this, it shows a very distinct check mark symbol, indicating everything would be alright and what the user sees is correct.
Looking at what the website reports, the data is completely different, however:
This is not a new bug. I have observed this behaviour many months ago already. I think going back as far as when I first used the Apple Health app integration for my water goal.