Draw two perfectly parallel lines straight across a paper.
Draw the same two perfectly parallel lines across a paper as a curve as well.

Let one line be the outer rim edge - let the other line be the inner wall edge.

Those lines represent a perfect extrusion before rolling and after rolling. When rolled into a perfect circle, substantively you have a perfectly round rim. Symptomatically, you also have an ERD that will be the same all the way around. Consistent ERD at multiple locations is not a meausure of a round rim, it is simply an ERD.

Now pick one line in each pair - and make it wiggly. Doesn't matter which one...you pick.

Now you have an extrusion with defects.

Let's say you chose the outer edge - try to true that out - all you do is transfer it to the inner wall edge - and voila! - you have uneven spoke tensions...

Let's say you already chose the inner wall edge - then it is automatically a true wheel with uneven spoke tensions...

But it get's worse....imagine it's 43mm deep in profile and triple wall just like a....

...wait for it....

...

...

...a Velocity B43. That is one incredibly stiff rim that requires an incredible amount of force to roll - making the need for a consistent extrusion even more important to begin with to ensure a quality rim.

You can true out a little extrusion error and lack of roundness from a classic double wall 16mm deep rim as FBinNY stated, but you can't do that with a Velocity B43.

Velocity put a lot of money into that line, they're a pain to produce right, and hence why they cost so much.

If you pay attention at all, I'm sure you've noticed that Weinmann Trak Attacks, and other B43 copies such as H+Son's can be all over the map tension-wise...now you know the reason without me saying it outright.

Note that H+Son's best rim extrusion and roundness wise is...their classic style TB14...their only rim I like.

=8-)