"obviously when child is at cm they cant do anything but if they observe this behaviour at home or in the presence of family etc then they must make sure their dc understands that it is wrong and wont be tolerated"
Fine, but maybe they are already. Or perhaps they have never witnessed the behaviour. Then what?
If one of your children became a biter, what would you actually do? My 14/nearly 15 month old understands the word no, as did my son at around the same age, but they are not necessarily compliant all the time - how many times have I told her not to chew the fireplace stones!!! So I say, "NO!" and move her away and all of that but I have to accept it will probably be several weeks or months before she will actually leave them alone on her own accord and I'd hazard a guess it will be more to do with the fact that developmentally she's moved on and no longer interested in them and that possibly it had nothing to do with me saying no (or may have done, but enough time passes in between that it can become hard to know what actually fixed things)
Children of that age can start to be diciplined for sure - or guided into correct behaviour - but it can take a bit of time and patience before they actually display those corrected, preferable behaviours. That's why I said it would be a different thing if it was still going on at 2 or 2 and a half - in fact, a load of development goes on between 18 months and 2 years from what I remember with the boy, hell, its the difference between a tiny tot and a proper little person. They still will not always do as told though - but at 2 years old its not necessarily down to parenting either.
I do accept that other parents would find it unacceptable, absolutely (I've had biting and hitting issues in that my son was a "victim" but neither of my kids have ever done it) so I'm all for a non-violent environment. I just feel that realistically at 16 months the CM will just have to supervise more closely, have a playpen for the child to be separated if necessary which doubles up as a time out type punishment if she has to go and prepare lunch...I dont know, but I feel she should be doing more than passing the buck and calling time.