It kinda makes sense when you think about it. Amphibiuos landing craft wouldn't be invented for another 800 years. I guess for the sake of gameplay, it makes sense to allow for invasions without ports at the receiving end, but for transfers?

..... Okay boys, we've cleared the channel. That's Normandy there, we're about 1/4 mile off shore. We can't get any closer because of the underwater rock formations. Over the side you go. Would you be so kind as to deliver this letter to my cousin while you're over there?.....