Ten days in transit is long enough that the plants could totally dry out even if watered right before shipping. They might require a substantial amount of soil to supply even a plant-in-a-box for that long. I got some small seedlings from Europe that spent 10 days in transit and they arrived okay but they had a lot more soil than a small seedling would typically be potted in.
I agree with you that 1yr plants should be bigger, though!
You might be better off buying 10-20 seeds, so you can be assured at least a few plants as these seem to really more than one to get a significant crop. I have three mature seedling pitangatubas and I still get very poor yield despite many flowers.