I have to agree with him. All of the science points to the fact that there was once an inland sea covering much of North America. I can take anyone in Dallas to see white rock outcroppings that show without a doubt that the sedimentation layers were laid down along a long period of time -- not a single, global flood.
Furthermore, if all of the fossils were laid down in a single flood event, we would expect a uniform mixture of fossils. We don't find that. Instead, we find fossilized species grouped in specific layers -- the same layers that we find all over the world.
Did Noah's flood happen? Absolutely -- the Bible tells us so. Did it cover the entire planet? No. The Bible says that it covered eretz -- a word that can mean anything from a local region to the land of Israel (the most common usage) to the entire planet.
God's revelation to us through his creation is no less truthful than his revelation to us through his word. God's creation overwhelmingly tells us that the flood did not cover the entire planet. Since the Bible does not require the entire planet to be covered by a universal flood, then we should not force an arbitrary meaning to a word in the Bible.
I'm not a YEC, but this statement does not follow from anything else you said.