If you put some amount of flickables allowing flicking in horizontal direction into one flickable allowing flicking in vertical direction and then try to scroll using two fingers gesture (https://support.apple.com/en-us/HT204895), it will work either only for nested flickables (macOS 10.12.1) or only for parent flickable (Linux Mint 17.1), even though if you press and drag, you'll be able to scroll in both directions.
I found this issue when I was implementing a such complex grid layout for smart TV using List Views, later I tried to do the same with pure Flickables and got the same result. I'm attaching two examples demonstrating the described behavior, one for Flickable and another for ListView to this issue. Funny that the behavior is different on Linux and macOS, but wrong in both cases.