I certainly noticed. In other threads, I think others have mentioned it also.
Initially, I was a little disappointed, but I realize that she didn't thank her sister, etc., like she did in her previous three Thank Yous. Seems like she kept them limited to only those who had done some hands-on work for ROTR, or in Edmund's case, a song written for them. And remember that ROTR isn't like her previous three records, as this one was "super arts and crafts time." You typically thank the teacher, not the onlooker.