I've owned the Garmin Index Smart Scale since February 2018. Prior to that I used an alternative scale that measured body fat, lean body mass etc. and saved all of this into Apple Health on my iOS device.
Initially, after getting the settings right in Apple Health, the Index Smart Scale worked as expected; weight, body fat% and BMI all synced from Garmin Connect into Apple Health. (The fact that Skeletal Muscle Mass isn't available to Apple Health as Lean Body Mass is annoying... but not new!)
However, since June Body Fat% is no longer syncing. Weight and BMI continue to come into Apple Health, but Body Fat no longer does.
I've tried all the usual troubleshooting tasks; Disconnecting and reconnecting Connect from Apple Health data sources, re-installing Connect, removing My Fitness Pal as a 3rd Party app... nothing has solved this.
Given the NTP scale issues, I'm about ready to consider this product a very expensive joke. Smart? No... anything but smart.