I read that sentence in the September-October issue of Archaeology magazine, in an article about rescue archaeology of a 17th-century wreck on North Carolina's Outer Banks. It indicated that in that era some trees were forced to grow in a curved shape. But as I read more tonight, it appears that shipbuilders could also find trees with natural curves in branches or trunks, and then harvest those for the necessary ship parts.
Re restoring Old Ironsides: "While the long, straight-grained white-oak planks are used for hull planking, the live oak's large branch sections and odd shapes are required for knee supports, breasthooks in the prow, and curving "compass timbers."
From a naval history website: "Oaks from the areas of Northern Europe were fine for the development of long straight planking, but the gnarled English "Hedgerow" Oak was the best for the natural curved timbers used to strengthen the ship internally. Trees were even deliberately bent in certain ways so as to " grow" a needed set of curved timbers. These curved timbers were known as "compass" timbers.
And one more note - in a book about harvest Brazilian timber for the shipbuilding industry, it was noted that dense forests contain tall straight trees, while more open stands have trees with more curving branches. But also of special value were the trees that have buttressed roots (banyan-like, I suppose), because those buttresses were curved in just the way that was required for some ship parts (but required extraordinary work to harvest because not only did the tree have to be felled, but the buttress root had to be dug out of the earth). You learn something every day.
The embedded image is from page 96 of Ship Modeling from Stem to Stern by Milton Roth, via Google Books.