Why is English Draughts double round robin?

3rd championship has started, 17 players double rr, so 32 games per player!

I think this is the only championship that is double rr instead of single rr?

Double round robin is needed due to the 3-move opening selection, some of which are not balanced.  This is the standard way of organizing tournament of English Checkers.

What I don't understand is why 17 players in draughts.cv.ENG.3.1.1 instead of 8 players and creating a 9 players draughts.cv.ENG.3.2.1

The system automatically tries to create a second layer with at least two tournaments. However, 9 players is not enough for two ch level tournaments, so it just puts all the remaining players in first league (which in this case happens to be a large number of players). If I've understood the system correctly, if there had been one more participant, 3.2.1 and 3.2.2 tournaments would have been created.