rofl you actually tried it!!!!!
Either unlock portrait orientation lock in control center or the app doesn't support landscape orientation.
It works for me, though I noticed a few times I had to jiggle it to get it to trigger.
I wish they would enable this on the 6. The plus is too big for my tastes, but I find myself browsing the web, watching video in landscape mode quite a bit, would love if the home screen rotated too.