It's just my thoughts but yes, I agree with you. In my workplace secondments are not at all unusual and, whilst secondees usually remain in their seconded role after the secondment period is complete, my understanding is that the agreement is temporary and bilaterally agreed as such.
It may be a case of 'musical chairs' however. When the music stops the person holding the redundant position may be the casualty. But I wouldn't have thought so since such a practice could be easily abused.