I agree that any different-depth etched look isn't right for American guns (particularly the very apparent different depths that were used on some German guns of the 19th century).

However, I've been fortunate to handle some very high-original condition guns, and have one set of late 1890s Parker D grade damascus bbls in high-original condition (obviously done by the original Parker factory process). There have been no detectable (to the naked eye, anyhow) depth differences in any of these.