Hope you are well today. As a new/sealed collector nothing annoys me more than used hardware being passed off as new,
It's tricky, I wouldn't sell it as new on ebay if I'd opened it and tested it. But that is an auction, if it's old and sealed then the buyer is taking that risk.
With the way that petro is selling them then he should be testing them, so I'd expect the box to be opened. You don't know what has happened to them in the warehouse they've been sitting in though.
If they turn up and look good and have the right keyboard then I don't see the problem. AFAIK they are the uglier amiga technologies badged ones though.
The price is better than I picked up a NOS magic pack for that had been sitting in a shop for a year after AT went under.
We have all had to replace drive belts on old computers, did they even do that?
3.5" drives don't have belts. The spindle is directly connected to the motor.