It won't be legal in all the states between NY and wherever you grow it. And transporting it across state lines opens you up to interdiction/legal trouble from the Feds. That's why they have to grow it near the consumers.

The marijuana thing shouldn't make sense, you're right - intensive lettuce growing systems don't translate to hemp well at all. Height, root structure, nutrient needs, schedule, and practically everything else vary and mess up your structure.

As other people here have pointed out, they really are growing lettuce. If they wanted to be ready to switch to hemp, they'd be using a closer analogue like tomatoes.