So right now the copia will replant anything that you are harvesting. Howevver since the copia does not drop seeds along side the wheat it makes it aggrivatingly difficult to farm wheat using the copia.  It isn't a limitation in the coding of the tool becaues the sky copia drops both wheat and seeds. 

It would be nice if the Wilder Copia would drop at least one seed when you mine mature wheat plants

The team reviewed this idea yesterday and noted that several people asked for this feature. It's going to be recommended and moved up the chain! If I hear more I'll update you; hopefully this would be an easy change that someone can take care of soon! 

This might be a bit late, but maybe the copia could use wheat to plant instead of a seed. Like it can take one wheat from the player's inventory for every seed it plants. It would solve the problem of getting seeds and the problem of replanting. Just a thought :)