Not entirely true, with an astrisk... Apple made some major improvement with the Series 6. The Series 5 and older might still be janky if they did not retroactively apply the improvements or if they were specific to the latest hardware.

Even the Series 6 still has course smoothing, but it is a lot closer to a legit GPS watch.

The root problem, I believe, is that Apple takes far fewer GPS readings to extend battery. The result was that they had to use software to try to guess the gaps in between the GPS readings. This was really bad for a while. It is better now, but I think they are still accuracy-limited by the infrequent GPS readings (you can see it in AWS6 course plotting). The other wild card is whether these course accuracy improvement algorithms only apply to the native workout app or if 3rd party apps get them too. If 3rd party apps to not have access to Apple's improved course approximation algorithms, then their GPS accuracy could righteously suck. Or not. It would depend on the app.

The other AW problem, which I do not think they resolved, is that the watch will not get its GPS lock until you begin an activity. So, it can go a while before locking, and then the watch retroactively does course corrections based on accelerometer activity. Sometimes this looks OK. Sometimes it is massively jacked up. And again, this works for the native app, but it could be ugly if 3rd party apps do not get the retroactive course corrections.