Vlad Please, allow me to try again.
I'd argue a tab is very similar to a folder in Finder. One would expect that clicking on it opens its contents, and everything else related can be done by interacting with it in some other way (clicking on the name to edit, or dragging to move are great examples).
In case of folders, the placement of the folder name clearly shows two things:
1, the name belongs to the folder it is under/next to
2, the name is not related to any other folder (as each folder has its own, and they move around with their folder)
I believe that there exists a subconscious expectation that the tabs and their urls have a similar relationship as folders and their names. When they added compact tabs to Safari, it felt very intuitive and easy to use for this exact reason; the update moved the only thing that was previously separated from the tabs to a place that shows and follows the above relationship.
I believe that the current compact tabs implementation in Orion throws off this inner expectation, both in the UI sense (I find the visuals to be confusing, similar to what the others described in this thread), and in the UX sense (I always have think for a fraction of a second before being able to use the url bar, whereas in Safari it's where I expect it to be)
The current implementation also takes up way more precious horizontal space than in Safari (can comfortably use 15 tabs in Safari whereas in Orion it's only 10 provided the same amount of characters is visible in tab names), and I believe this to be an objective downside.
I do agree that the HIG is generally a great guideline for building good user interfaces and experiences, but they're just that, guidelines. The changes in Safari highlight that there are instances where not following the HIG is the best practice, from an UI and UX standpoint. The fact that so many users enjoy it and are asking for something similar clearly differentiates it from the new System Settings, for example, which illustrates that yes, the HIG is there for a reason, and in most cases should be followed.
I hope I my points could illustrate why the compact tabs are not such a case.