I’d also have to say, my watch 6 appears to be about as accurate as my Garmin for running, I did notice on 1 ride when I was recording with both my watch and my bike computer that the watch was behind a few hundred meters, but I think that may have had something to do with the forest as my garmin has both GPS and a speed sensor to use so it’s quite probable that it can compensate for weak signal.
As for running I been running the same routes for years, when I’m road running at least and the distances are always on par, I never expect any commercial GPS to be 100% accurate. Was planning on selling the Garmin when I get my Ultra and actually mounting the ultra to the bike, but may run them both for a while, will be interesting to compare data.