You are right. OTOH @chanath is not being very accurate:
dock is just a fork with less options.
The options are all there, just not exposed in Tweaks. A few of them, supported by Ubuntu, are exposed in the Settings app (Gnome Control Center). The other ones are exposed via dconf, you might use “dconf Editor” if you prefer a GUI.
Why should anyone needs a car without few tires?
Because Canonical isn’t interested in maintaining a “combinatorial explosion” of settings, so they offer just the basic ones as officially supported. They don’t prevent you from tweaking dconf settings or installing the full extension, though (indeed, their design deliberately supports this capability).
I highly recommend https://didrocks.fr/2017/08/18/ubuntu-gnome-shell-in-artful-day-5/ for more accurate information on the original design.