I think it has to do with the mandate of Jess and Simon to get their own book. Unfortunately they can't expand the books into more than 2 books, due to the lack of sales. It's upsetting by the fact that Van Jensen did lots of interesting things with John and when these other writers take over, they act like it never happened or existed. The editorial management is awful. John Stewart should've been the head of the GLC while Hal was leading in GL.
They can exist at the same time, but that's not what DC or what these writers wants. Gabriel Hardman could've used both John and Hal (I mean, why not? Aren't they both going to be co-leads in the GLC movie?), but it's always one over the other. So I have no interest in purchasing anything like that.
About him working on the GL movie could be the reason why he decided to use Hal.