shule1, to me the difference is the amount of moisture inside the seed itself, not so much the external moisture. It would make sense to me, that if the seed has had no chance to dry somewhat before it freezes, it would be the expansion of ice crystals inside the seed in the embryo that would "explode" or damage those cells so they die. If a seed is very dry, there is no moisture inside to expand so freezing can't harm them.
Worth, hard to say - wiki does say
Plant seeds or shoots may be cryopreserved for
conservation purposes. But that sounds like just for looking at them, not that they would necessarily be functioning after thawing.