Yesterday, I enabled my auto-update setting to allow update of my FR255 (non-music) from 17.x to 18.23 firmware.
From the time when Garmin Connect on my Google Pixel 5a started showing that it was transferring the update to the watch, it took more than an hour and consumed roughly 15-20% of my phone battery in the process. The phone was otherwise idle and sitting only a foot away from the watch, which I was charging at the same time. Normally, it would not even show a 1% decrease during such a period.
Why is this so slow and power-hungry? I know from experience that bluetooth can transfer files to other devices relatively quickly and without meaningful power drain on the phone.