In summary, fresh clam chowder is expected to have a small amount of sand in it due to the nature of fresh clams being filter feeders. The speaker suggests a method of purging the sand from live clams before cooking them. This technique does not work for "prairie oysters."
Is fresh clam chowder expected to have a tiny bit of sand in it (from the clams)? I'm only familiar with the canned versions of clam chowder. Many of them contain a little sand.
When I lived in Maine we would sometimes eat steamed mussels and steamer clams. To purge the sand I would keep them live in the fridge in salted water and feed them sprinkles of corn muffin mix for a couple of days. The critters would expell the sand and fill their tummies with sweet muffin mix. Yum.
As a midwesterner I can advise that the same technique does not work for "prairie oysters".