Looking at mine for comparison, I noted that (being the same part) the coil spring pockets are reversed left to right - so you see the lower part of the pocket on the right at the rear (where the end of the spring sits), and on the left that lower part is in the front.
That makes that area look tilted (since it is actually tilted) when comparing the two from the rear.
from your picture, the center & top of the arm look even - and that's the part that would be "level" when comparing the two.
I'd be unhappy about those tabs myself, but since they aren't a tight fit to the eccentrics normally, your guess that the compression of the bolt on the washers & spacer is what actually holds things in place once tightened is likely correct.
They DO help a lot when aligning it, since twisting the eccentrics against the tabs moves things sideways to change the alignment setting...