This thread shows the photo used for that Wiltse card and the other T206 "sweater" portraits of New York Giants:
http://www.net54baseball.com/showthread.php?t=219861
As you can see from the photo, the Giants did have sweaters with a two-part pattern like that shown on the card. But Wiltse was standing behind Cy Seymour in the picture, so the artist had to reconstruct his sweater for the card, and he didn't do a very good job lining up the buttons.