I think it's a pretty shitty move for the fans to split the series that far apart time-wise.
The reason(s) I think they are doing that is because:
It's the last season and they want to milk it for all it's worth
They can release an 8-episode DVD/BR set for the same price as a regular season
It can be sold a week or two before the last half of the final season
Then they can sell the next half for the same price before releasing it as a "entire season set" for a couple bucks above the price of half the season... before making an entire box set.
I hope I'm wrong, but I am sure a lot of the reason is greed.
It would make more sense if it was a 4-6 month hiatus. But then it would fuck up the timing of sales release(s).