Connecting rooms are never guaranteed - even if your reservation says "guaranteed connecting rooms". People have arrived to find that they do NOT have connecting rooms despite having been assured by Disney CM's that they will. Even in circumstances where it is more than just something that you would like, but is actually a need, connecting rooms are not always possible. So, if you really need to be in the same space, it is wise to book DVC or some such place that keeps you all together without a connecting rooms request. Handicapped people and elderly people and children (all requiring care) have been put in non connecting rooms from their care givers. I have read/heard multiple angry reports of people with these type scenarios. It is sometimes a problem.
However, every effort is made to accommodate peoples needs first and wishes as well. SO, if you do need a connecting set of rooms, your odds are better that you will get it if you request them. Most people given a 'guarantee' will arrive to find that they DO have connecting rooms. So they then state that their connecting rooms were guaranteed.
It just makes sense until you happen to be one of the ones that learn the hard way "connecting rooms are not guaranteed" after all. Hence the confusion.