Interesting. My 2015 37ND has two openings on the floor of that compartment. It has the larger for the waste hose and then to the left of that about 9 inches away is a smaller one (approx 3 inches in diameter) for the fresh water hose. The one for fresh water is a hinged cover rather than screw in and it has a slot so that the cover can be closed while the hose is installed.
They can be seen in the attached pic.
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