If you compare the shirt sizes for women and kids, they are nearly the same. In a Women’s XL size Chest Width is 18-3/4", a Kids’s Shirt 12 yrs size the Chest Width is 17-5/8"
Just for reference, I compared the women's regular size charts from Lands End and their sizes are very different.
Assuming that the woot shirts chest width figure is doubled, there is 5-6 inches difference between shirts. For instance, a woot small is 15" across or 30" around, a Lands End small t-shirt is 35 inches!