It was fairly unusual for top Singles skaters from North America and Asia, but not so unusual for top skaters from Europe. Check out Carolina Kostner's Competitive Highlights section on Wikipedia, for example. Or Kiira Korpi's.Agree. Prior to the Challenger Series, top elites doing a senior B was fairly unusual. I think Tuk was one of the people who popularized going to them and winning with her run up to the 2015 World title.
At the time, all or almost all of the Senior B's were in Europe, so they were easy to get to from somewhere like Oberstdorf or Tampere, but not so easy from Lake Arrowhead or Nagoya.