The parallel winds are interesting for sure. And they can be based on any of the winds as I understand it. I have read of it being used on ABC and dLRK winds too. I thought at first that it was only two windings in parallel but now understand that three or move can be used. That is sometimes referred to as YYY, DDD, etc.
Here is a thread that has some interesting discussion on it, it touches on some of the complexities of how parallel winds on different motors changes the kV's and the like: