How smooth should I expect final finish to be on an new hardwood floor install?
There are standards for the installation of hardwood floors. The national association that is commonly used is the MFMA
https://www.maplefloor.org/TechnicalInfo/Finishes-Sealers.aspx
While their name has “maple” in it, it is also qualified to examine and review other species, such as birch, oak, etc.
I’ve given you a link that shows many members, but I’d scroll to the bottom for MFMA’s main home office in Illinois. I’d start there. They can refer you to a reputable investigator. You’ll probably have to pay to get someone to review the work and prepare a written evaluation.
It looks bad enough to me to require it be re-sanded, re-stained and re-sealed.