Not really, quite simple why it happens.
If a team has a great first half of season, and then a bad one. It's the downward trend, everyone starts to wonder if the manager can turn it around, it all appears to be going wrong, chairman think better get in someone else who can do it.
If a team has a bad first half, the chairman will be thinking can he turn it around, already thinking about replacing him. Then suddenly he does turn it round, storming finish to season, it's an upward trend, this is great it will continue, great job!
Despite finishing on the same amount of points, they will look at how they think the future will go based on the most recent results.
Not that I'm saying Adkins should be sacked if we have a **** 2nd half, just I can easily see why it happens that way!