> while the solid wood used for the steps between levels began showing visible wear only a few months after installation.

The wood used matters, and the way it's finished matters a lot, with hardwood floors. You can get anything between amazingly-resilient and scratches-badly-if-you-look-at-it-funny, depending on how it's finished.

Lots of contractors cheap out on the finish, and pre-finished hardwood is pretty much always bad.