If you analyse it a little, if I multiply the odds of the 4 SL clubs each being promoted, it totals up as Evens.
Looked at that way, it means the bookies think it is as likely that one will drop as it is that all four will stay up.
One of them will almost certainly be in the playoff game, whatever they do, so I suppose as a SL group, evens is about right.
If a Championship club gets the miracle of automatic promotion then that can only be Leigh, and if they don't then they will certainly be in the playoff, so Evens sounds about right to me.
Thinking about it, I don't think the overall picture of the odds is showing a huge gulf at all, it is reflecting that there is a very real chance that Leigh will oust a SL team and at the start of the season, I would not have said that would be an even money shot. But with the demise of Wakey and Salford it is at least genuinely on the cards.