It's because they consider the knots to be a natural "beautiful" part of working with wood. I think Scott specifically mentioned that the knot in that picture looked like a "rose". That said, if he were building a bass for you from scratch, he would let you know/give you a choice as to whether or not you'd accept a knot.
The vast majority of the couple hundred Birdsongs out there do not have visible knots in the wood...
when mine was made, some "imperfections" showed in the wood as he sanded them down... He sent me pics and asked what I thought and I thought it just made the wood interesting and gave it character, which he agreed, and continued building. I love the knots and swirls in the wood. Some of my favorite axes he has made are the 2nd (I think) annivesary pecan basses... beautiful.


