...yes and? One is brand new and the other's used. Why would they take apart a unit that was just put together hours ago? Every component going into a Mac is checked regardless, that's why you'll find every brand new Mac's got at least one battery charge cycle and a couple hundred GB written to the SSD already. You make it sound as if Apple just ships these new units to customers and hopes they'll turn on.
Every refurbished Mac was once a new Mac, and I'd rather have the unused new hardware. With iPhones and iPads at least you get a new battery and a new housing, with Macs it's really just a used device that was inspected and cleaned by Apple. I buy both brand new from Apple and used from craigslist and never had a single issue with either one and we have more than a dozen Macs in the family.
If a brand new device really has an issue out of the box that wasn't caught it still makes more sense to make the customer exchange it rather than doing labor intense manual QC on every single unit leaving the factory in order to keep cost down. It's the customer who would have to pay for it.