No way to know for sure, I guess. My only problem with these would be that you really don’t know why these have not been used by the factory.
If you can check them thoroughly and the price is good, then sure. Go for it. Lay them on a flat surface and see if they’re perfectly flat and not warped in any way. If you have a spoke and nipple at hand, check if the spoke holes have been evenly drilled and are oriented/angled correctly in alternating directions. Weigh them both to see if there’s any weird difference in weight between the two.
Apart from that, you could obviously also just get any similar looking carbon rim with the same ERD from a reliable seller. There’s many options discussed here on the forum. AFAIK these Giant rims are pretty dated in their design anyway.
