It is very common in my area to just put a pipe in and smoosh the clay in around it and let it go at that...no real compacting, no thought of seep prevention, BUT we have excellent clays and moderate seasons. My small pond has a 15" corrugated drain pipe and the clay fill was just tapped in with a backhoe bucket...it does not seep a drop.
In your case, I would have to rely on the builder that is familiar with your area and, more specifically, your pond location. If they have a good reputation, guarantees the work, and says you don't need a seep collar then I would consider that good professional advise. The most important part of this is their reputation.
Welcome to the forums BTW,
