I wondered about the septic SOP, too. In this case, it sounds like you won’t have to “excavate” it or “uncover” it, since it’s sitting out in the open?
So you need to walk that fine line between wanting to help your friend, versus your level of experience with this type of system. Don’t get in over your head, but at the same time, try to be helpful. It could end up just being a case where you have to say, “I don’t know.” There’s nothing wrong with that when it comes to alternative systems. After you’ve seen it, you could tell your friend that you’ll try to find more info, and get back to him.
Is the person who installed it available to help?
And yes, it makes sense that it would need a venting system of some sort. I’ll be interested to hear more about it after you have seen it.