If it wasn't obvious from the main series, in NS I think it's fair to say Moiraine is absolutely obsessed with her height and how it compares to everybody else's. And as Jeo pointed out, being short is described as a defining trait for Cairhienin in general.

This casting does suggest they will take quite a lot of liberty with such aspects of the books - but then, they were always going to do that, as well as cutting various semi-major characters entirely or combining several roles into one.