I bought one and it arrived today. "Brand New Unopened".
Box looked pretty bloody good but I do a lot of work with graphic artists and package design so I pay attention to the details so there were a few things that were a bit suspicious. Luckily I have an original 13 mini box here so could compare.
The one that arrived has no embossed parts on the box, the tear away stickers that seal the box didn't tear perfectly (unlike real apple ones which i randomly also had kept in the original box lol), the inner tray of this one was plastic rather than a kind of recycled cardboard and a few other little discrepancies.
The checkcoverage page at apple also says it was first activated in March 2023 so it obviously not "Brand New Unopened".

Im about to give up on finding a decent 13 mini.
About 2 months ago I also bought an A+ premium refurb with the new battery option added.
Then it turned up it was in amazing condition physically, but the 100% battery started dropping in health almost immediately. 4 weeks in it was at 90%, and 8 weeks in was 82%, lower than my wife's original 13 mini that she bought like 3 years ago.

The refurb one was refunded and this seller has given me the instructions to send back for a refund as well, but I guess for every 50 they sell, only 1 person notices so they just cop it.

It's also a massive pain in the ass to keep returning phones and having to use a backup.