overhead for INSERTS using change tracking and/or change data capture (CDC)
Yes it makes sense, CDC is maintained via a Log Reader, which other than the overhead of the reads on the log drive, and the writes to the capture tables, should not affect the insert rate. They're thinking about (old school :)) tracking via triggers, which can easily impact the insert rate.

But to be safe, make sure your tests run long enough for the overhead of the reader to be actively capturing the inserts.