I still have am almost new set of welded, anodized rims from a road bike from the late 80's.
The braking surface was never machined, as was normal for that time frame, and the rim clearly shows a wave effect with minimal high spots where the swaging process for the nipple eyelet distorted the rim microscopicly. So the anodizing has worn off at 32 equally spaced high spots around the rim and the wave effect has always caused shuddering at medium and low speed braking. In some respects - we're very spoiled today. Even inexpensive rims now have machined braking surfaces.