Did you see a week or two ago the story about Jackson Pollock's name being woven-painted into one of his paintings? I don't see why this comes as a surprise to people --unless they're people who've never created things themselves. Who doesn't sneak their name into things they've made?
Back when I cross-stitched, my initials were always hidden in the lower right corner. Needlepoint too. Even my first free motion quilting (the photo above) has my initials in cursive in the border. I don't think anyone else can tell what they are, but I know they're there (going sideways). It's just fun to do.