This isn’t actually my experience. The best riders get in the woods at a sprint and typically they will settle into a race pace. Yes you have to be fit enough to keep up with the main group or else my advice doesn’t matter as you aren’t competing for a podium anyways. And if you can’t go fast and stay on the bike it also doesn’t matter.
Obviously I have no idea what his goals are. If he wants to podium, do what I suggested. If he is just looking to finish, there is plenty of good advice here.