They are Lands, not Parks.
He's just estimating the 6 months. DLR has basically an entire year of a head start on 'real' work done on SWL. It will be open in DLR early 2019. I can even see soft openings in 2018. They were targetting late 2018 as a possible opening date if everything went smoothly. While it looks like it has, its much easier to market 'Coming in 2019' for both then to say 'Well, ones coming in late 2018 and the other sometime in 2019.'
SWL at DHS (or whatever its called then) will be much later in 2019, and some have said maybe 2020.
The problem is, with people like Fresh Baked Disney able to do updates of the DLR progress, its much harder to do updates of the DHS progress (I guess the PizzaRizzo balcony gives some decent shots, though) but the progress at DLR is much, much further along. They haven't even finished all the demo at DHS yet.