These container tops all appear to have been filled in with faded light yellow paint, that I think is typical of the earliest stages of construction; there is no sign of vertical parallel hatching; some have rows of dots around them; all are very simple.
My belief is therefore that the five circles in the NW rosette were originally drawn as free-standing circles (and please don’t ask me what this pattern means, because I don’t know), and that the pipe bodies (and the five central dark areas inside the circular ends, to make them resemble pipe tops) connecting them to the rosette were added afterwards.
I think this also implies that the pipes all around the central rosette don’t have any actual meaning, but were rather added to try to draw attention away from the five fake pipes in the NW rosette.
The two most common angle units are the ones we all know and hate, degrees (deg) and radians (rad).
Anyway, if you're one of the many (myself included) who have been nervous about rotations because it means unwieldy units and frustrating math, I have good news: CSS actually has four different units for angles, and the other two are, IMHO, much easier to work with.
Let's look at some common angles compared between degrees, radians, and gradians (all rounded to 2 decimal places).
And I think that's easier with gradians and turns, even for the common angles.
Looking at the table again, I probably wouldn't want to use turns if I'm doing a lot of animating within a single quadrant.
On the other end of the spectrum, I'd much rather use turns for anything larger than a single quadrant, especially one you rotate more than a single full circle.