If it was replaced threw the genius bar, it was a replacement unit. (Could be new, could be new with reused parts harvested from returned devices) I worked as a genius for more years than I like to admit. The phone you got is good. I have owned several replacement units over the years. If you have problems apple will fix them.

>exchange the Covered Equipment with a replacement product that is new or comprised of new and/or previously used genuine Apple parts and has been tested and passed Apple functional requirements. All replacement products provided under this Plan will at a minimum have the same or substantially similar features (e.g., a different model with the same features, or the same model in a different color) as the original product. If Apple exchanges the Covered Equipment, the original product becomes Apple’s property and the replacement product is your property, with coverage effective for the remainder of the Plan Term. Apple may use Covered Devices or replacement parts for service that are sourced from a country that is different from the country from which the Covered Device or original parts were sourced.

https://www.apple.com/legal/sales-support/applecare/applecareplus/2209/220907_applecareplus_us.pdf