You voiced concern with the builder, and that is a good thing. To have that in writing would be excellent, but may not be possible. I would take many photos to record all this, and do so as the pond fills. Once its underwater, hard to show where problems may be.

Hang tight and wait to see the outcome. Hopefully you did the good homework on finding this builder. If you hire a sheepsfoot roller to come in, you are taking on that added expense. If the first guy was really cheap, well that may not hurt so much. I think bringing in someone else would tend to null the original builder out of any liability to make it right, if there is a problem.

How big of a pond will it be? Easy enough to drain down and rework it? Might hold off stocking anything to expensive in case it has to be reworked.