Phoned first thing this morning and spoke to a guy who checked and double checked. Happily the news was as I originally thought - couldn't imagine that they would send people from the immigration department to a new migrants info session and lie to them! The spouse can do the work requirement and then can become the main applicant for the 887 visa. They will not be required to do a skills assessment as one will have been done for the original main applicant and it is not needed again (even though the applicants have swapped places so to speak.)
I hope no one introduces more panic over this subject as it has caused real worry at this end, and although I was convinced that what I had always been told must be right, it is still scary until you get the pr, particularly when you are halfway there and fear that it may have been time wasted etc.. I'm sure nobody intended to stir up a hornet's nest, however people must check their facts and be clear about exactly which visa they are referring to (the rules can be different accordingly).
Hope all the 495ers who were upset about this have a better night sleep tonight!