The other alternate idea of a leading expanding diagonal published up to yesterday will be discarded based upon a very low probability.
An analysis back to 1997 of the daily chart of first waves and A waves at minor degree* and above reveals 23 examples, and all but one were impulses. The sole leading diagonal found was contracting for a first wave up, so it does appear that leading expanding diagonals are not very common.
* One wave at minute degree is included as it was the start of a long third wave.
Thanks for the separate post. Will be good to keep your “special” analysis and research in an easy accessible location for future reference.