I don't like people who sell used things as new.
if this has never been used and just taken out of the box to check on and has been taken out and tested, and is being stated as such then that is no problem imho, as long as everyone knows, it is for all intends and purposes still new.
(technically it isn't new anyways, since it is several decades old)
I'd rather have something that has been tested to work and provided pictures than buy the literal cat in a sack.
if it got damaged or scuffed while taking out and testing, then of course this has to be stated honestly.
of course the argument can be made that something that is still sealed is worth more to a fancy collector.
the problem here is simply peoply lying, but wether it has been taken out of the box or not doesn't make a shred of a difference there, because someone willfully lying will just reseal the box, hell there's people rewrapping things to make them "new" again.
I'd rather have someone honest sell me something that they know is new than someone asking a huge markup just because it is still sealed.