We could certainly discuss the writing tools used by Johns in the Rebirth special. But he did have both Manhattan's mechanization and the HUAC hearings in the issue. And using that as well as the Chekov's gun aspect of Johnny's scene gives it some importance. Now if that has changed with editorial manipulations, it MIGHT be different. But it seems to make a lot more sense to think that actual story content is more important than cynical speculation.
Jay and Wally having Speed Force stays is a tough one to work through without knowing what writers are thinking. But Wally remembers a scene with Jay and Jay remembers a relationship with Barry in The Button. A Jay that the DC Universe remembers is alluded to twice (maybe more depending on what is happening in Flash.
DClock has had severe timeliness problems. But with an issue scheduled for August, it's no surprise DC isn't soliciting an issue of a bi-monthly comic for September. I expect a solicit for DClock #12 with October's books. As to the Green Lantern thing, Alan Scott being the alpha of the golden age JSA crew, that is pretty much a James Robinson idea from Golden Age and Earth 2. Manhattan saw the shift in characters and relative importances with the JSA in DClock (reading books helps) and a removal of GL from the golden age makes some story sense. Johns may very well have a GL fixation, but the consensus seems to be that Alan Scott's a substitute for Clark Kent.