According to Tips and Notes, "Unlike -na- tense, the hu- aspect marker does not take a subject prefix instead it must be preceeded by a noun or a personal pronoun."
If this is true, the correct answer should be "Yeye hucheza", right?
"Must be" is a bit strong. It can be left out if context is clear enough, but yeah, it should definitely accept yeye hucheza*.
I couldn't answer it better, yes hu- means the same thing. But also "Hucheza", had double meaning, it means he/she plays or dances.