Well, it’s a magic world! Most things are possible! Sure, from a realistic standpoint this doesn’t make sense. But Erica (our MC) has been adapting to being in a fantasy world and is hoping for what would be impossible in reality. And it seems like (from the most recent chapter) that the seeds can be revived from their dormant state. (I said “dormant” because the blue-haired kid said that there was still life in the seeds in their dried states.)
The seeds are expired but she'd trying to find the "magic spell" that can revive them, which is definitely possible in a magical world, I guess
I might not know much about growing plants, but this kind of bothers me. Rice is Grown in flooded fields and seeds do have an expiration date. You can't just grow something from damaged seeds. Like for someone aiming to be a farmer they should know that. especially since they seemed to be aiming for rice in particular.