I have been playing around with the page layout on my IPad Pro and discovered that is is impossible to group apps if you leave an empty space in the page. I found the option fun to finally place my apps where i want and not just lined up from top to bottom.
I discovered if you leave gaps in the page layout it is impossible to groupe apps. The moment you hover the app over the groupe, the groupe shifts back to fill the empty space. Once I filled up all the empty space then the groupe stops moving. It is pretty annoying.
The was excited to see the new feature to finally hate it completely. I do hope someone will fix this problem.
For help with iPad Pro, please post in the Apple Support Community. The Apple Developer Forums are for questions about APIs and features intended specifically for developers.