They were just sent in the small plastic ziploc you can see on the photo, in a padded envelope sent by regular mail.
Since it came from France it just took two days so the packaging wouldn't really matter, I don't know how they store them on their side, or how long, and I think that's what would matter most. Or where they get them from.
In my experience when citrus seeds are stored dry, at first it only makes them longer to germinate but doesn't really affect germination rate until at least a few weeks or maybe a couple of months. And maybe Citrus glauca seeds are also better at withstanding this, since they are a desert plant.
I received them on 14 September so they took between two and three weeks to germinate.